1.
PSO-1
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The PSO-1 is a telescopic sight manufactured in Russia by the Novosibirsk instrument-making factory and issued with the Russian military Dragunov sniper rifle. The PSO-1 was, at the time of its introduction around 1964, the PSO-1 was specifically designed for the SVD as a telescopic sight for military designated marksman activities. The current version of the sight is the PSO-1M2 and this telescopic sight is different from the original PSO-1 only in that it lacks the now obsolete infrared detector. The metal body of the PSO-1 is made from a magnesium alloy, the PSO-1 features a battery-powered red illuminated reticle with light provided by a simple diode bulb. It features professionally ground, fully multi-coated optical elements, an enamel finish for scratch protection. The scope body is sealed and filled with nitrogen, which prevents fogging of optics and was designed to function within a -50 °C to 50 °C temperature range. For zeroing the sight the reticle can be adjusted by manipulating the elevation. Considered the higher end of Soviet military side-mount telescopic sights, the quality of the PSO-1 is higher than most other PSO-style telescopic sights, the PSO-1 has neither a focus adjustment nor a parallax compensation control. Most modern military tactical scopes with lower power fixed magnification such as the ACOG, modern fixed magnification military high-end-grade sniper telescopic sights scopes intended for long-range shooting usually offer one or both of these features. The positioning of the body to the left of the bore’s center line may not be comfortable to all shooters. The PSO-1 elevation turret features bullet drop compensation in 50 m or 100 m increments for engaging point, at longer distances the shooter must use the chevrons that would shift the trajectory by 100 m per each chevron. The BDC feature must be tuned at the factory for the ballistic trajectory of a particular combination of rifle. Inevitable BDC-induced errors will occur if the environmental and meteorological circumstances deviate from the circumstances the BDC was calibrated for, marksmen can be trained to compensate for these errors. The PSO-1 features a reticle with floating elements designed for use in range estimation and bullet drop, the top center chevron is used as the main aiming mark. The horizontal hash marks are for windage and lead corrections and can be used for ranging purposes as well, to the left is a stadiametric rangefinder that can be used to determine the distance from a 1.7 meters tall object/person from 200 m to 1000 m. For this the lowest part of the target is lined up on the horizontal line. Where the top of the target touches the top curved line the distance can be determined and this reticle lay out is also used in several other telescopic sights produced and used by other former Warsaw Pact member states. The three lower chevrons in the center are used as hold over points for engaging targets beyond 1,000 meters
2.
Dragunov sniper rifle
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The Dragunov sniper rifle is a semi-automatic sniper/designated marksman rifle chambered in 7. 62×54mmR and developed in the Soviet Union. For that reason, it was originally named Самозарядная Винтовка системы Драгунова образца1963 года Self-Loading Rifle, System of Dragunov and it was selected as the winner of a contest that included three competing designs, by Sergei Simonov, Aleksandr Konstantinov and Yevgeny Dragunov. Extensive field testing of the rifles conducted in a range of environmental conditions resulted in Dragunov’s proposal being accepted into service in 1963. An initial pre-production batch consisting of 200 rifles was assembled for evaluation purposes, since then, the Dragunov has become the standard squad support weapon of several countries, including those of the former Warsaw Pact. Licensed production of the rifle was established in China and Iran, the Dragunov is a semi-automatic, gas-operated rifle with a short-stroke gas-piston system. The barrel breech is locked through a rotating bolt and uses three locking lugs to engage corresponding locking recesses in the barrel extension, the rifle has a manual, two-position gas regulator. A gas regulator meters the portion of the gases fed into the action in order to cycle the weapon. The gas regulator can be set with the help of the rim of a cartridge, the normal position #1 leaves a gas escape port opened in the form of a hole that lets some combustion gas escape during cycling. Position #2 closes the gas port and directs extra combustion gas to the piston increasing the recoil velocity of the gas-piston system. It is used for when the rifle does not reliably cycle due to carbon fouling build-up in the gas port, when shooting in extreme cold or high altitude or using low powered ammunition. After discharging the last cartridge from the magazine, the bolt carrier, the rifle has a hammer-type striking mechanism and a manual lever safety selector. The firing pin is a type and, as a result. Thus, military-grade ammunition with primers confirmed to be seated is recommended for the Dragunov. This appears to have solved the slam fire issue, the rifles receiver is machined to provide additional accuracy and torsional strength. The Dragunovs receiver bears a number of similarities to the AK action, such as the large dust cover, iron sights and lever safety selector and these cosmetic similarities can lead to mis-categorization of the Dragunov as an AK variant. The barrel profile is relatively thin to save weight and is ended with a flash suppressor. The barrel’s bore is chrome-lined for increased resistance, and features 4 right-hand grooves. It is not rifled over its length but partly over a length of 547 mm
3.
Bell & Howell
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Bell & Howell is a U. S. -based former manufacturer of motion picture machinery, founded in 1907 by two projectionists, and headquartered in Wheeling, Illinois. The company now provides inserting and finishing solutions for letters and parcels, document processing, microfilmers, scanners, the Bell & Howell trademark is also licensed to makers of various electronic consumer products. According to its charter, the Bell & Howell Company was incorporated on February 17,1907 and it was duly recorded in the Cook County Record Book eight days later. The first meeting of stockholders took place in the office of Attorney W. G, strong on February 19 at 10 a. m. The first board of directors was chosen for a term of one year, Donald Joseph Bell, chairman, Albert Summers Howell, secretary, austin Delaney was president of Bell and Howell in Canada in the 1960s and 1970s before moving with his family from England. Historically, Bell & Howell Co. was an important supplier of many different media technologies, the firm dropped the production of movie cameras in the early 1970s. Bell & Howell is a supplier of equipment for schools. The film laboratory line is now a company, BHP Inc. The firm added microfilm products in 1946 and it purchased University Microfilms International in the 1980s. UMI produced a product called ProQuest, in the 2000s, Bell and & Howell decided to focus on their information technology businesses. The imaging business was sold to Eastman Kodak and the mail business was sold to Pitney Bowes. On June 6,2001 Bell & Howell became ProQuest Company, which was then a publicly traded company, in September 2001, the remaining industrial businesses, along with the Bell & Howell name, were sold to private equity firm Glencoe Capital. The company merged with the North American arm of Böwe Systec Inc, in 2003, Böwe Systec later acquired the entire company. It was known as Böwe Bell & Howell until 2011, when Versa Capital Management bought the company from bankruptcy and they also had an Electronics and Instrumentation Division on Lennox Road, Basingstoke, UK. This facility produced several different types of transducers for applications such as North Sea oil platforms, the modified Apple had additional security elements for classroom use such as a tamper-proof cover. The case color was black but the inside was a standard Apple II Plus, Bell & Howell founded an Education Group within their company in 1907. This Education Group created Bell & Howell Schools in 1966, in that same year, the Education Group purchased a controlling share of DeVry Institute of Technology. Two years later in 1968, Bell & Howell’s Education Group, via a controlling interest in DeVry, acquired Ohio Institute of Technology in Columbus, over the years, the Education Group has bought and sold large interests in a variety of educational organizations and institutions
4.
Gridiron (cooking)
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A gridiron is a metal grate with parallel bars typically used for grilling meat, fish, vegetables, or combinations of such foods. It may also be two such grids, hinged to fold together, to hold food securely while grilling over an open flame, early examples of the gridiron were found in Pompeii. The Latin term is craticula, a form of crates. This referred to their design, which appeared similar to a wicker basket. This is also used as the base for the term graticule, there were numerous iron gridirons manufactured and patented in the U. S. in the 1800s. Originally called spiders, these iron legged devices were used in a fireplace placed over the fire to cook food, over time, gridirons have been developed specifically to accommodate the type of food being prepared and the cooking method being used. A combination hinged gridiron and spider was developed and patented in 1836 by Amasa and George Sizer of Meriden, a steel wire gridiron was developed and patented as early as 1889 in New Haven, Connecticut, by William C. Perkins, of the New Haven Wire Goods Co. who received a U. S, patent #408,136 for a hinged gridiron that would hold the meat in place while broiling. A commercial hinged broiler or gridiron was designed for use in the Bridge & Beach and this hinged broiler was manufactured by Luigi Pieragostini, also of the New Haven Wire Goods Co. and patented in 1939, U. S. Today, hinged gridirons are used extensively to deep fry or broil fast food in restaurants throughout the world, hotdog gridirons are also available for camping and outdoor cooking. Gridirons are essential to Chapter 28 of David Copperfield when David, the American football and Canadian Football fields resembles a gridiron, which brought up the term gridiron football. In Christian iconography the gridiron is an attribute of Saint Lawrence of Rome, the Italian Experience In New Haven, Images And Oral Histories. A Guide To American Trade Catalogs 1744-1900
5.
Telescopic sight
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A telescopic sight, commonly called a scope, is a sighting device that is based on an optical refracting telescope. They are equipped with some form of graphic image pattern mounted in an appropriate position in their optical system to give an accurate aiming point. Telescopic sights are used all types of systems that require accurate aiming but are most commonly found on firearms. Other types of sights are iron sights, reflector sights, the optical components may be combined with optoelectronics to form a night scope. The first experiments directed to give shooters optical aiming aids go back to the early 17th century, for centuries different optical aiming aids and primitive predecessors of telescopic sights were created that had practical or performance limitations. The first documented telescopic rifle sight was invented between 1835 and 1840, in 1855, William Malcolm of Syracuse, NY began producing his own sight. Malcolm used a design incorporating achromatic lenses like those used in telescopes. They were between three and twenty magnification, malcolms and those made by L. M. Amidon of Vermont were the standard during the Civil War. Still other telescopic sights of the same period were the Davidson. An early practical refractor telescope based telescopic sight was built in 1880 by August Fiedler, later telescopic sights with extra long eye relief became available for handgun and scout rifle use. A historic example of a sight with a long eye relief is the German ZF41 which was used during World War II on Karabiner 98k rifles. An early example of a man portable telescopic sight for low visibility/night use is the Zielgerät 1229, the ZG1229 Vampir was a Generation 0 active infrared night vision device developed for the Wehrmacht for the StG44 assault rifle, intended primarily for night use. The issuing of the ZG1229 Vampir system to the military started in 1944, Telescopic sights are classified in terms of the optical magnification and the objective lens diameter, e. g. 10×50. This would denote 10 times magnification with a 50 mm objective lens, in general terms, larger objective lens diameters, due to their ability to gather larger amounts of light, provide a larger exit pupil and hence provide a brighter image at the eyepiece. On fixed magnification sights the magnification power and objective diameter should be chosen on the basis of the intended use, there are also telescopic sights with variable magnification. The magnification can be varied by manually operating a zoom mechanism, variable sights offer more flexibility regarding shooting at varying ranges, targets and light conditions and offer a relative wide field of view at lower magnification settings. The syntax for variable sights is the following, minimal magnification – maximum magnification × objective lens, for example, 3–9×40. Confusingly, some older telescopic sights, mainly of German or other European manufacture, have a different classification where the part of the designation refers to light gathering power
6.
Oscilloscope
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Other signals can be converted to voltages and displayed. Oscilloscopes are used to observe the change of a signal over time, such that voltage. The observed waveform can be analyzed for such properties as amplitude, frequency, rise time, time interval, distortion, modern digital instruments may calculate and display these properties directly. Originally, calculation of these values required manually measuring the waveform against the scales built into the screen of the instrument, the oscilloscope can be adjusted so that repetitive signals can be observed as a continuous shape on the screen. A storage oscilloscope allows single events to be captured by the instrument and displayed for a long time. Oscilloscopes are used in the sciences, medicine, engineering, automotive, general-purpose instruments are used for maintenance of electronic equipment and laboratory work. Special-purpose oscilloscopes may be used for purposes as analyzing an automotive ignition system or to display the waveform of the heartbeat as an electrocardiogram. Early oscilloscopes used cathode ray tubes as their display element and linear amplifiers for signal processing, storage oscilloscopes used special storage CRTs to maintain a steady display of a single brief signal. CROs were later superseded by digital storage oscilloscopes with thin panel displays, fast analog-to-digital converters. DSOs without integrated displays are available at lower cost and use a digital computer to process. The basic oscilloscope, as shown in the illustration, is divided into four sections. The display is usually a CRT or LCD panel which is out with both horizontal and vertical reference lines referred to as the graticule. In addition to the screen, most display sections are equipped with three controls, a focus knob, an intensity knob and a beam finder button. The vertical section controls the amplitude of the displayed signal and this section carries a Volts-per-Division selector knob, an AC/DC/Ground selector switch and the vertical input for the instrument. Additionally, this section is equipped with the vertical beam position knob. The horizontal section controls the base or sweep of the instrument. The primary control is the Seconds-per-Division selector switch, also included is a horizontal input for plotting dual X-Y axis signals. The horizontal beam position knob is located in this section
7.
Microscope slide
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A microscope slide is a thin flat piece of glass, typically 75 by 26 mm and about 1 mm thick, used to hold objects for examination under a microscope. Typically the object is placed or secured on the slide, and this arrangement allows several slide-mounted objects to be quickly inserted and removed from the microscope, labeled, transported, and stored in appropriate slide cases or folders. Microscope slides are used together with a cover slip or cover glass. These sliders were popular in Victorian England until the Royal Microscopical Society introduced the standardized glass microscope slide, a standard microscope slide measures about 75 mm by 25 mm and is about 1 mm thick. A range of sizes are available for various special purposes, such as 75 x 50 mm and for geological use,46 x 27 mm for petrographic studies. Slides are usually made of glass and their edges are often finely ground or polished. Microscope slides are made of optical quality glass, such as soda lime glass or borosilicate glass. Fused quartz slides are used when ultraviolet transparency is important. While plain slides are the most common, there are specialized types. A concavity slide or cavity slide has one or more shallow depressions, designed to hold slightly thicker objects, if this system were used with a slide which did not incorporate these cut-off corners, the corners would chip and the slide could shatter. A graticule slide is marked with a grid of lines that allows the size of objects seen under magnification to be easily estimated, sometimes one square of the grid will itself be subdivided into a finer grid. Slides for specialized applications, such as counting, may have various reservoirs, channels. Various permanent markings or masks may be printed, sand-blasted, or deposited on the surface by the manufacturer, some slides have a frosted or enamel-coated area at one end, for labeling with a pencil or pen. Slides may have special coatings applied by the manufacturer, e. g. for chemical inertness or enhanced cell adhesion, the coating may have a permanent electric charge to hold thin or powdery samples. Common coatings include poly-L-lysine, silanes, epoxy resins, or even gold, the mounting of specimens on microscope slides is often critical for successful viewing. The problem has given much attention in the last two centuries and is a well-developed area with many specialized and sometimes quite sophisticated techniques. In a dry mount, the simplest kind of mounting, the object is placed on the slide. A cover slip may be placed on top to protect the specimen and this mounting can be successfully used for viewing specimens like pollen, feathers, hairs, etc
8.
Vertical bar
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The vertical bar is a computer character and glyph with various uses in mathematics, computing, and typography. It has many names, often related to particular meanings, Sheffer stroke, verti-bar, vbar, stick, broken bar, vertical line, vertical slash, bar, glidus, obelisk, or pipe. The vertical bar is used as a symbol in absolute value, | x |, read the absolute value of x. set-builder notation. Often a colon, is used instead of a vertical bar, sometimes a vertical bar following a function, with sub- and super-script limits a and b is used when evaluating definite integrals to mean f from a to b, or f-f. A vertical bar can be used to separate variables from fixed parameters in a function, examples, | ψ ⟩, The quantum physical state ψ. ⟨ ψ |, The dual state corresponding to the state above, ⟨ ψ | ρ ⟩, The inner product of states ψ and ρ. A pipe is a communication mechanism originating in Unix, which allows the output of one process to be used as input to another. In this way, a series of commands can be piped together, in most Unix shells, this is represented by the vertical bar character. For example, grep -i blair filename. log | more where the output from the process is piped to the more process. The same pipe feature is found in later versions of DOS. This usage has led to the character itself being called pipe, in many programming languages, the vertical bar is used to designate the logic operation or, either bitwise or or logical or. Specifically, in C and other languages following C syntax conventions, such as C++, Perl, Java and C#, since the character was originally not available in all code pages and keyboard layouts, ANSI C can transcribe it in form of the trigraph. Which, outside string literals, is equivalent to the | character, in regular expression syntax, the vertical bar again indicates logical or. For example, the Unix command grep -E fu|bar matches lines containing fu or bar, the double vertical bar operator || denotes string concatenation in PL/I, standard ANSI SQL, and theoretical computer science. Although not as common as commas or tabs, the bar can be used as a delimiter in a flat file. Examples of a standard data format are LEDES 1998B and HL7. It is frequently used because vertical bars are typically uncommon in the data itself, similarly, the vertical bar may see use as a delimiter for regular expression operations. This is useful when the expression contains instances of the more common forward slash delimiter
9.
Concentric objects
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In geometry, two or more objects are said to be concentric, coaxal, or coaxial when they share the same center or axis. Circles, regular polygons and regular polyhedra, and spheres may be concentric to one another, in the Euclidean plane, two circles that are concentric necessarily have different radii from each other. However, circles in three-dimensional space may be concentric, and have the radius as each other. For example, two different meridians of a terrestrial globe are concentric with each other and with the globe of the earth, more generally, every two great circles on a sphere are concentric with each other and with the sphere. The circumcircle and the incircle of a regular n-gon, and the regular n-gon itself, are concentric, for the circumradius-to-inradius ratio for various n, see Bicentric polygon#Regular polygons. The region of the plane between two circles is an annulus, and analogously the region of space between two concentric spheres is a spherical shell. For a given point c in the plane, the set of all circles having c as their forms a pencil of circles. Each two circles in the pencil are concentric, and have different radii, every point in the plane, except for the shared center, belongs to exactly one of the circles in the pencil. Every two disjoint circles, and every hyperbolic pencil of circles, may be transformed into a set of circles by a Möbius transformation. The ripples formed by dropping an object into still water naturally form an expanding system of concentric circles. Evenly spaced circles on the used in target archery or similar sports provide another familiar example of concentric circles. Coaxial cable is a type of cable in which the combined neutral. Johannes Keplers Mysterium Cosmographicum envisioned a system formed by concentric regular polyhedra. Concentric circles are found in diopter sights, a type of mechanic sights commonly found on target rifles. They usually feature a disk with a small-diametre hole near the shooters eye. When these sights are aligned, the point of impact will be in the middle of the front sight circle. Centered cube number Homoeoid Focaloid Circular symmetry Magic circle Geometry, Concentric circles demonstration With interactive animation
10.
Chevron (insignia)
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A chevron is an inverted V-shaped pattern. The chevron occurs in early art including designs on pottery and rock carvings, examples can be found approximately 1800 BC in archaeological recovery of pottery designs from the palace of Knossos on Crete in the modern day country of Greece. Sparta used a capital lambda on their shields, a chevron is one of the ordinaries in heraldry, one of the simple geometrical figures which are the chief images in many coat of arms. It can be subject to a number of modifications, when the ends are cut off in a way that looks like the splintered ends of a broken piece of wood, with an irregular zig-zag pattern, it is called éclaté. When shown as a smaller size than standard, it is a called a chevronel. Chevrons appeared early in the history of heraldry, especially in Normandy, in Scandinavia the chevron is known as sparre, an early example appears in the arms of Armand desmondly. In areas observing Commonwealth of Nations or United States doctrine, chevrons are used as an insignia of enlisted or NCO rank by military forces, one chevron usually designates a lance corporal, two a corporal, and three a sergeant. One to four rockers may also be incorporated to indicate various grades of sergeant, in American usage, chevrons typically point towards the neck, in Commonwealth usage they usually point away from the neck. In the Commonwealth, the terminology for rank chevrons includes the number of stripes, called bars, therefore. Canadian and Australian Forces often refer to chevrons as hooks, in the Dutch armed forces they are nicknamed bananas. In some armies, small chevrons are worn on the left sleeve to indicate length of service. The Israel Defense Forces use chevrons in various orientations as organizational designators on their vehicles, specifically which company within a battalion they belong to
11.
Firearm
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A firearm is a portable gun - a barreled weapon that launches one or more projectiles, often driven by the action of an explosive force. The first primitive firearms originated in 13th-century China when the fire lance was combined with projectiles. The technology gradually spread through the rest of East Asia, South Asia, older firearms typically used black powder as a propellant, but modern firearms use smokeless powder or other propellants. Most modern firearms have rifled barrels to impart spin to the projectile for improved flight stability, modern firearms can be described by their caliber or in the case of shotguns their gauge, by the type of action employed together with the usual means of deportment. The word firearms usually is used in a sense restricted to small arms, shooters aim firearms at their targets with hand-eye co-ordination, using either iron sights or optical sights. The accurate range of pistols generally does not exceed 100 yards, while most rifles are accurate to 550 yards using iron sights, some purpose-built sniper rifles are accurate to ranges of more than 2,200 yards. The smallest of all firearms is the handgun, there are three common types of handguns, single-shot pistols, revolvers, and semi-automatic pistols. Revolvers have a number of firing chambers or charge holes in a revolving cylinder, semi-automatic pistols have a single fixed firing chamber machined into the rear of the barrel, and a magazine so they can be used to fire more than one round. Each press of the fires a cartridge, using the energy of the cartridge to activate the mechanism so that the next cartridge may be fired immediately. This is opposed to double-action revolvers which accomplish the end using a mechanical action linked to the trigger pull. Prior to the 19th century, virtually all handguns were single-shot muzzleloaders, with the invention of the revolver in 1818, handguns capable of holding multiple rounds became popular. Certain designs of auto-loading pistol appeared beginning in the 1870s and had largely supplanted revolvers in military applications by the end of World War I. By the end of the 20th century, most handguns carried regularly by military, police and civilians were semi-automatic, both designs are common among civilian gun owners, depending on the owners intention. A long gun is any firearm that is larger than a handgun and is designed to be held. Early long arms, from the Renaissance up to the century, were generally smoothbore firearms that fired one or more ball shot. Most modern long guns are either rifles or shotguns, both are the successors of the musket, diverging from their parent weapon in distinct ways. A rifle is so named for the spiral fluting machined into the surface of its barrel. Shotguns are predominantly smoothbore firearms designed to fire a number of shot, shotguns are also capable of firing single slugs, or specialty rounds such as bean bags, tear gas or breaching rounds
12.
Graphical user interface
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GUIs were introduced in reaction to the perceived steep learning curve of command-line interfaces, which require commands to be typed on a computer keyboard. The actions in a GUI are usually performed through direct manipulation of the graphical elements, beyond computers, GUIs are used in many handheld mobile devices such as MP3 players, portable media players, gaming devices, smartphones and smaller household, office and industrial controls. Designing the visual composition and temporal behavior of a GUI is an important part of application programming in the area of human–computer interaction. Its goal is to enhance the efficiency and ease of use for the logical design of a stored program. Methods of user-centered design are used to ensure that the language introduced in the design is well-tailored to the tasks. The visible graphical interface features of an application are sometimes referred to as chrome or GUI, typically, users interact with information by manipulating visual widgets that allow for interactions appropriate to the kind of data they hold. The widgets of an interface are selected to support the actions necessary to achieve the goals of users. A model–view–controller allows a structure in which the interface is independent from and indirectly linked to application functions. This allows users to select or design a different skin at will, good user interface design relates to users more, and to system architecture less. Large widgets, such as windows, usually provide a frame or container for the main presentation content such as a web page, smaller ones usually act as a user-input tool. A GUI may be designed for the requirements of a market as application-specific graphical user interfaces. By the 1990s, cell phones and handheld game systems also employed application specific touchscreen GUIs, newer automobiles use GUIs in their navigation systems and multimedia centers, or navigation multimedia center combinations. Sample graphical desktop environments A GUI uses a combination of technologies and devices to provide a platform that users can interact with, a series of elements conforming a visual language have evolved to represent information stored in computers. This makes it easier for people with few computer skills to work with, the most common combination of such elements in GUIs is the windows, icons, menus, pointer paradigm, especially in personal computers. The WIMP style of interaction uses a virtual device to represent the position of a pointing device, most often a mouse. Available commands are compiled together in menus, and actions are performed making gestures with the pointing device, a window manager facilitates the interactions between windows, applications, and the windowing system. The windowing system handles hardware devices such as pointing devices, graphics hardware, window managers and other software combine to simulate the desktop environment with varying degrees of realism. Smaller mobile devices such as personal assistants and smartphones typically use the WIMP elements with different unifying metaphors, due to constraints in space
13.
Cursor (user interface)
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The mouse cursor is also called a pointer, owing to its resemblance in usage to a pointing stick. A cursor is the given to the transparent slide engraved with a hairline that is used for marking a point on a slide rule. The term was transferred to computers through analogy. In text mode displays, it was not possible to show a bar between characters to show where the new text would be inserted, so an underscore or block cursor was used instead. In situations where a block was used, the block was created by inverting the pixels of the character using the boolean math exclusive or function. On text editors and word processors of modern design on bitmapped displays, in a typical text editing application, the cursor can be moved by pressing various keys. These include the four keys, the Page Up and Page Down keys, the Home key, the End key. The position of the cursor also may be changed by moving the pointer to a different location in the document. The blinking of the cursor is usually temporarily suspended when it is being moved, otherwise. In this way, a block cursor may be seen as a piece of selected text one character wide, in some cases, the cursor may split into two parts, each indicating where left-to-right and right-to-left text would be inserted. The I-beam pointer is a cursor shaped like the capital letter I, the purpose of this cursor to indicate text can be highlighted, inserted, or changed. The pointer or mouse cursor echoes movements of the device, commonly a mouse. This kind of cursor is used to manipulate elements of user interfaces such as menus, buttons. It may be called a pointer, because the mouse is the dominant type of pointing device used with desktop computers. The idea of a cursor being used as a marker or insertion point for new data or transformations, such as rotation, blender, for instance, uses a 3D cursor to determine where future operations are to take place. A real-life cursor such as this was featured as a character in the science fiction TV series Automan. Susan Kare, designer of several of the common cursor shapes Creating and controlling browser cursors Cross-browser CSS custom cursors Installing A Cursor On Your Computer
14.
Robert Hooke
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Robert Hooke FRS was an English natural philosopher, architect and polymath. Allan Chapman has characterised him as Englands Leonardo, Robert Gunthers Early Science in Oxford, a history of science in Oxford during the Protectorate, Restoration and Age of Enlightenment, devotes five of its fourteen volumes to Hooke. Hooke studied at Wadham College, Oxford during the Protectorate where he became one of a tightly knit group of ardent Royalists led by John Wilkins. Here he was employed as an assistant to Thomas Willis and to Robert Boyle and he built some of the earliest Gregorian telescopes and observed the rotations of Mars and Jupiter. In 1665 he inspired the use of microscopes for scientific exploration with his book, based on his microscopic observations of fossils, Hooke was an early proponent of biological evolution. Much of Hookes scientific work was conducted in his capacity as curator of experiments of the Royal Society, much of what is known of Hookes early life comes from an autobiography that he commenced in 1696 but never completed. Richard Waller mentions it in his introduction to The Posthumous Works of Robert Hooke, the work of Waller, along with John Wards Lives of the Gresham Professors and John Aubreys Brief Lives, form the major near-contemporaneous biographical accounts of Hooke. Robert Hooke was born in 1635 in Freshwater on the Isle of Wight to John Hooke, Robert was the last of four children, two boys and two girls, and there was an age difference of seven years between him and the next youngest. Their father John was a Church of England priest, the curate of Freshwaters Church of All Saints, Robert Hooke was expected to succeed in his education and join the Church. John Hooke also was in charge of a school, and so was able to teach Robert. He was a Royalist and almost certainly a member of a group who went to pay their respects to Charles I when he escaped to the Isle of Wight, Robert, too, grew up to be a staunch monarchist. As a youth, Robert Hooke was fascinated by observation, mechanical works and he dismantled a brass clock and built a wooden replica that, by all accounts, worked well enough, and he learned to draw, making his own materials from coal, chalk and ruddle. Hooke quickly mastered Latin and Greek, made study of Hebrew. Here, too, he embarked on his study of mechanics. It appears that Hooke was one of a group of students whom Busby educated in parallel to the work of the school. Contemporary accounts say he was not much seen in the school, in 1653, Hooke secured a choristers place at Christ Church, Oxford. He was employed as an assistant to Dr Thomas Willis. There he met the natural philosopher Robert Boyle, and gained employment as his assistant from about 1655 to 1662, constructing, operating and he did not take his Master of Arts until 1662 or 1663
15.
William Gascoigne (scientist)
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William Gascoigne was an English astronomer, mathematician and maker of scientific instruments from Middleton, Leeds who invented the micrometer. He was one of a group of astronomers in the north of England who followed the astronomy of Johannes Kepler which included, Jeremiah Horrocks, Gascoigne was born in Middleton, Leeds in 1611, the son of a minor country gentleman. His father was Henry Gascoigne, Esq. of Thorpe-on-the-Hill in the parish of Rothwell, near Leeds and his mother was Margaret Jane, daughter of William Cartwright. Little is known of his early life and he claimed he was educated at the University of Oxford, although no record of this has been found. When he looked through the arrangement Gascoigne saw the web bright and he then added this arrangement to a sextant modelled on the instrument used by Tycho Brahe, although Tycho’s sextant was only a naked-eye instrument. Gascoignes sextant was five feet in radius, and measured the distance between astronomical bodies to a degree of accuracy. Gascoigne then realised that by introducing two points, whose separation could be adjusted using a screw, he could measure the size of the image enclosed by them, Gascoigne met the Lancashire astronomer William Crabtree, probably in 1640. After making observations at Gascoignes home, Crabtree was much taken with these inventions, on his return to his home in Broughton, just outside Manchester, he wrote to Gascoigne asking if he might obtain such instruments and also wrote to his friend Jeremiah Horrocks about them. I beseech you Sir, slack not your Intentions for the Perfection of your begun Wonders, sadly, Horrocks died before he could try out the instruments, but Crabtree and Gascoigne did use them to try to corroborate Horrockss theories about the elliptical orbit of the Moon. This invention was taken up and improved by the scientist. Towneley later brought the instrument to the attention of Robert Hooke, the micrometer, as it became known, was to lie at the heart of astronomical measurement down to the twentieth century. In 1642, civil war broke out in England, and Gascoigne received a commission as Providore for Yorkshire in the army of King Charles I, Crabtree lived in Broughton, just outside Manchester which was on the parliamentary side and all correspondence between the two ceased. Gascoigne died at the Battle of Marston Moor, Yorkshire, on 2 July 1644 as did Charles Towneley, after Gascoignes death some of his papers and fragments of correspondence between Crabtree and Gascoigne came into the possession of Christopher and Richard Towneley. He began his massive three-folio volume Historia Coelestis Britannica by printing five pages of their letters and observations. Chapman, A. Transits of Venus, History Results and Legacy Goward, Jeremiah Horrocks and the Transit of Venus Sellers, David. A Letter from William Gascoigne to Sir Kenelm Digby, cambridge, England, Science History Publications Ltd. pp. 405–416. In Search of William Gascoigne, Seventeenth Century Astronomer
16.
Film
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A film, also called a movie, motion picture, theatrical film or photoplay, is a series of still images which, when shown on a screen, creates the illusion of moving images due to the phi phenomenon. This optical illusion causes the audience to perceive continuous motion between separate objects viewed rapidly in succession, the process of filmmaking is both an art and an industry. The word cinema, short for cinematography, is used to refer to the industry of films. Films were originally recorded onto plastic film through a photochemical process, the adoption of CGI-based special effects led to the use of digital intermediates. Most contemporary films are now fully digital through the process of production, distribution. Films recorded in a form traditionally included an analogous optical soundtrack. It runs along a portion of the film exclusively reserved for it and is not projected, Films are cultural artifacts created by specific cultures. They reflect those cultures, and, in turn, affect them, Film is considered to be an important art form, a source of popular entertainment, and a powerful medium for educating—or indoctrinating—citizens. The visual basis of film gives it a power of communication. Some films have become popular worldwide attractions by using dubbing or subtitles to translate the dialog into the language of the viewer, some have criticized the film industrys glorification of violence and its potentially negative treatment of women. The individual images that make up a film are called frames, the perception of motion is due to a psychological effect called phi phenomenon. The name film originates from the fact that film has historically been the medium for recording and displaying motion pictures. Many other terms exist for a motion picture, including picture, picture show, moving picture, photoplay. The most common term in the United States is movie, while in Europe film is preferred. Terms for the field, in general, include the big screen, the screen, the movies, and cinema. In early years, the sheet was sometimes used instead of screen. Preceding film in origin by thousands of years, early plays and dances had elements common to film, scripts, sets, costumes, production, direction, actors, audiences, storyboards, much terminology later used in film theory and criticism apply, such as mise en scène. Owing to the lack of any technology for doing so, the moving images, the magic lantern, probably created by Christiaan Huygens in the 1650s, could be used to project animation, which was achieved by various types of mechanical slides
17.
Milliradian
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A milliradian, often called a mil or mrad, is an SI derived unit for angular measurement which is defined as a thousandth of a radian. Mils are used in adjustment of firearm sights by adjusting the angle of the sight compared to the barrel, Mils are also used for comparing shot groupings, or to compare the difficulty of hitting different sized targets at different distances. Using optics with mil markings in the one can make a range estimation of a known size target, or vice versa to determine a target size if the distance is known. In such applications it is useful to use a unit for target size that is a thousandth of the unit for range, for instance by using the metric units millimeters for target size and meters for range. This coincides with the definition of the milliradian where the arc length is defined as 1/1000 of the radius, a common adjustment value in firearm sights is 1 cm at 100 meters which equals 10 mm/100 m = 1/10 mil. The true definition of a milliradian is based on a circle with a radius of one. There are other definitions used for mapping and artillery which are rounded to more easily be divided into smaller parts. The milliradian was first used in the mid nineteenth century by Charles-Marc Dapples, degrees and minutes were the usual units of angular measurement but others were being proposed, with grads under various names having considerable popularity in much of northern Europe. However, Imperial Russia used a different approach, dividing a circle into equilateral triangles, around the time of the start of World War I, France was experimenting with the use of milliemes for use with artillery sights instead of decigrades. The United Kingdom was also trialing them to replace degrees and minutes and they were adopted by France although decigrades also remained in use throughout World War I. The United States, which copied many French artillery practices, adopted mils, before 2007 the Swedish defence forces used streck which is closer to the milliradian but then changed to NATO mils. After the Bolshevik Revolution and the adoption of the system of measurement the Red Army expanded the 600 unit circle into a 6000 mil one. Hence the Russian mil has a different origin than those derived from French artillery practices. In the 1950s, NATO adopted metric units of measurement for land, Mils, meters, and kilograms became standard, although degrees remained in use for naval and air purposes, reflecting civil practices. The approximation error by using the linear formula will increase as the angle increases. New shooters are often explained the principle of subtensions in order to understand that a milliradian is an angular measurement, subtension is the physical amount of space covered by an angle and varies with distance. Thus, the corresponding to a mil varies with range. Subtensions always change with distance, but a mil is always a mil regardless of distance, therefore ballistic tables and shot corrections are given in mils thereby avoiding the need of mathematical calculations
18.
Stadiametric rangefinding
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Stadiametric rangefinding, or the stadia method is a technique of measuring distances with a telescopic instrument. The term stadia comes from a Greek unit of length, stadiametric rangefinding is used for surveying and in the telescopic sights of firearms, artillery pieces, or tank guns, as well as some binoculars and other optics. It is still used in long-range military sniping, but in many professional applications it is being replaced with microwave, infrared. The stadia method is based upon the principle that in similar triangles homologous sides are proportional and this means that, for a right triangle with a given angle, the ratio of adjacent side length to opposite side length is constant. In either case, the parameter is used, in conjunction with the angular measurement. An object 5 meters high, for example, will cover 1 mrad at 5000 meters, or 5 mrad at 1000 meters, or 25 mrad at 200 meters. Since the radian expresses a ratio, it is independent of the units used, stadia readings used in surveying can be taken with modern instruments such as transits, theodolites, plane-table alidades and levels. When using the measuring method, a stadia rod is held so that it appears between two stadia marks visible on the instruments reticle. The stadia rod has measurements written on it that can be read through the telescope of the instrument, an instrument equipped for stadia work has two horizontal stadia marks spaced equidistant from the center crosshair of the reticle. The interval between stadia marks in most stadia instruments gives a stadia interval factor of 100, the distance between the instrument and a stadia rod can be determined simply by multiplying the measurement between the stadia hairs by 100. The instrument must be level for this method to work directly, if the instrument line of sight is inclined, the horizontal and vertical distance components must be determined. Some instruments have additional graduations on a circle to assist with these inclined measurements. These graduated circles, known as circles, provide the value of the horizontal. This system is sufficiently precise for locating topographic details such as rivers, bridges, buildings, the stadia method of distance measurement is primarily historical for surveying purposes, as distance nowadays is mostly measured by electronic or taping methods. Total station instruments do not have stadia lines marked on the reticle, traditional methods are still used in areas where modern instruments are not common or by aficionados to antique surveying methods
19.
Reflector sight
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These sights work on the simple optical principle that anything at the focus of a lens or curved mirror will look like it is sitting in front of the viewer at infinity. Since their invention in 1900, reflector sights have come to be used as gun sights on all kinds of weapons. They were used on aircraft, in a limited capacity in World War I, widely used in World War II. Reflector sights are used in civilian applications such as sights on surveying equipment, optical telescope pointing aids. The collimated reticle image can also be seen at any eye position in the volume of collimated light created by the sight behind the optical window. Eye movement perpendicular to the optical axis will make the reticle image move in exact relationship to eye position in the cylindrical column of light created by the collimating optics. A common type uses a lens and a beam splitter. This type tends to be bulky since it requires at least two components, the lens and the beam splitter/glass plate. The reticle collimation optics are situated at 90° to the optical path making lighting difficult, usually needing additional electric illumination, condensing lenses and this type is most often seen as the red dot type used on small arms. It is also possible to place the reticle between the viewer and the mirror at the mirrors focus. The reticle itself is too close to the eye to be in focus, the viewing portion of a reflector sight does not use any refractive optical elements, it is simply a projected reticle bounced off a beam splitter or curved mirror right into the users eye. This gives it the characteristics of not needing considerable experience and skill to use. The primary drawback of reflector sight is that they need some way to illuminate the reticle to function, reticles illuminated by ambient light are hard to use in low light situations, and sights with electrical illumination stop functioning altogether if that system fails. The idea of a reflector sight originated in 1900 with Irish optical designer and this arrangement would be of course equally impracticable for obvious reasons but it is instanced to show that a beam of light has the necessary qualifications for our purposes. It was noted soon after its invention that the sight could be an alternative to iron sights. The reflector sight was first used on German fighter aircraft in 1918, through their development in the 1930s and into World War II the sight was also being referred to in some applications by the abbreviation reflex sight. Reflector sights were invented as an improved gun-sight and since their invention they have adapted to many types of weapons. When used with different types of guns, reflector sights are considered an improvement over simple iron sights, the reflector sights single, parallax-free virtual image, in focus with the target, removes this aiming problem, helping poor, average, and expert shooters alike
20.
FN P90
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The FN P90, also known as the FN Project 1990, is a personal defense weapon designed and manufactured by FN Herstal in Belgium. Featuring a compact design with an integrated reflex sight and fully ambidextrous controls. Its design incorporates several innovations such as a unique top-mounted magazine and FNs small-caliber, high-velocity 5. 7×28mm ammunition. The P90 is currently in service with military and police forces in over 40 nations, such as Austria, Brazil, Canada, France, Greece, India, Malaysia, Poland, and the United States. In the United States, the P90 is in use with over 200 law enforcement agencies, while developed and initially marketed as a PDW, it can also be considered a submachine gun or compact assault rifle. The standard selective fire P90 is restricted to military and law enforcement customers, but since 2005, the P90 and its 5. 7×28mm ammunition were developed by FN Herstal in response to NATO requests for a replacement for the 9×19mm Parabellum cartridge and associated pistols and submachine guns. NATO called for two types of weapons chambered for a new cartridge—one a shoulder-fired weapon, and the other a handheld weapon. According to NATO, these new weapons, termed personal defense weapons, were to provide protection in last-resort situations when the user is directly endangered by the enemy. Additionally, it was to be capable of penetrating body armor, the shoulder-fired personal defense weapon was to weigh less than 3 kg, with a magazine capacity of at least 20 rounds. The handheld personal defense weapon was to weigh less than 1 kg, although a weight of 700 g was deemed desirable, the original 5. 7×28mm cartridge, called the SS90, went into production with the P90 in 1990. The SS90 propelled a 1.5 g plastic-core projectile from the P90 at a velocity of roughly 850 m/s. Shortly after its introduction, the P90 was adopted and used in service with the Belgian special forces group in the 1991 Gulf War, following the P90s introduction, FN revised the 5. 7×28mm ammunition. The new variation, designated the SS190, used a projectile 2.7 mm shorter in length than that of the SS90 and this allowed it to be used more conveniently in the 5. 7×28mm FN Five-seven pistol, which was under development at that time. The SS190 projectile had a weight, and a more conventional construction with an aluminium. The first prototypes of the SS190 were created in 1992, a modified version of the P90, with a magazine adapted to use the shortened ammunition, was then introduced in the same year. Several special cartridge variations were developed, such as the L191 tracer round, in 2002 and 2003, NATO conducted a series of tests with the intention of standardizing a PDW cartridge as a replacement for the 9×19mm Parabellum cartridge. The tests compared the merits of the FN5. 7×28mm cartridge and the HK4. 6×30mm cartridge. However, the German delegation and others rejected the NATO recommendation that 5. 7×28mm be standardized, as a result, both the 4. 6×30mm and 5
21.
Philippe de La Hire
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Philippe de La Hire was a French painter, mathematician, astronomer, and architect. According to Bernard le Bovier de Fontenelle he was an academy unto himself and he was born in Paris, the son of Laurent de La Hire, a distinguished artist and Marguerite Coquin. In 1660, he moved to Venice for four years to study painting, upon his return to Paris, he became a disciple of Girard Desargues from whom he learned geometrical perspective and was received as a master painter on August 4,1670. His paintings have sometimes confused with those of his son, Jean Nicolas de La Hire. He also began to study science and showed an aptitude for mathematics, from 1679–1682 he made several observations and measurements of the French coastline, and in 1683 aided in mapping France by extending the Paris meridian to the north. In 1683 La Hire assumed the chair of mathematics at the Collège Royal, from 1687 onwards he taught at the Académie d’architecture. La Hire wrote on methods,1673, on conic sections,1685, a treatise on epicycloids,1694, one on roulettes,1702. His works on conic sections and epicycloids were based on the teaching of Desargues and he also translated the essay of Manuel Moschopulus on magic squares, and collected many of the theorems on them which were previously known, this was published in 1705. He also published a set of tables in 1702. La Hires work also extended to descriptive zoology, the study of respiration, two of his sons were also notable for their scientific achievements, Gabriel-Philippe de La Hire, mathematician, and Jean-Nicolas de La Hire, botanist. Mons La Hire, a mountain on the Moon, is named for him, unless otherwise stated La Hires works are in French. In, Histoire de lAcadémie royale des sciences, p, La Hire, Philippe de la, vol. 2, pp. 662–664, in The Dictionary of Seventeenth-Century French Philosophers, oConnor, John J. Robertson, Edmund F. Philippe de La Hire, MacTutor History of Mathematics archive, University of St Andrews. Philippe de La Hire at the Catholic Encyclopedia This text incorporates public domain material from the Rouse History of Mathematics
22.
Diamond
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Diamond is a metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the rate from diamond to graphite is negligible at standard conditions. Diamond is renowned as a material with superlative physical qualities, most of which originate from the covalent bonding between its atoms. In particular, diamond has the highest hardness and thermal conductivity of any bulk material and those properties determine the major industrial application of diamond in cutting and polishing tools and the scientific applications in diamond knives and diamond anvil cells. Because of its extremely rigid lattice, it can be contaminated by very few types of impurities, such as boron, small amounts of defects or impurities color diamond blue, yellow, brown, green, purple, pink, orange or red. Diamond also has relatively high optical dispersion, most natural diamonds are formed at high temperature and pressure at depths of 140 to 190 kilometers in the Earths mantle. Carbon-containing minerals provide the source, and the growth occurs over periods from 1 billion to 3.3 billion years. Diamonds are brought close to the Earths surface through deep volcanic eruptions by magma, Diamonds can also be produced synthetically in a HPHT method which approximately simulates the conditions in the Earths mantle. An alternative, and completely different growth technique is chemical vapor deposition, several non-diamond materials, which include cubic zirconia and silicon carbide and are often called diamond simulants, resemble diamond in appearance and many properties. Special gemological techniques have developed to distinguish natural diamonds, synthetic diamonds. The word is from the ancient Greek ἀδάμας – adámas unbreakable, the name diamond is derived from the ancient Greek αδάμας, proper, unalterable, unbreakable, untamed, from ἀ-, un- + δαμάω, I overpower, I tame. Diamonds have been known in India for at least 3,000 years, Diamonds have been treasured as gemstones since their use as religious icons in ancient India. Their usage in engraving tools also dates to early human history, later in 1797, the English chemist Smithson Tennant repeated and expanded that experiment. By demonstrating that burning diamond and graphite releases the same amount of gas, the most familiar uses of diamonds today are as gemstones used for adornment, a use which dates back into antiquity, and as industrial abrasives for cutting hard materials. The dispersion of light into spectral colors is the primary gemological characteristic of gem diamonds. In the 20th century, experts in gemology developed methods of grading diamonds, four characteristics, known informally as the four Cs, are now commonly used as the basic descriptors of diamonds, these are carat, cut, color, and clarity. A large, flawless diamond is known as a paragon and these conditions are met in two places on Earth, in the lithospheric mantle below relatively stable continental plates, and at the site of a meteorite strike. The conditions for diamond formation to happen in the mantle occur at considerable depth corresponding to the requirements of temperature and pressure
23.
Chemical milling
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Chemical milling or industrial etching is the subtractive manufacturing process of using baths of temperature-regulated etching chemicals to remove material to create an object with the desired shape. It is mostly used on metals, though materials are increasingly important. It was developed from armor-decorating and printing etching processes developed during the Renaissance as alternatives to engraving on metal, most modern chemical milling methods involve alkaline etchants, these may have been used as early as the first century CE. Armor etching, using mineral acids, was not developed until the fifteenth century. Etchants mixed from salt, charcoal, and vinegar were applied to plate armor that had painted with a maskant of linseed-oil paint. The etchant would bite into the areas, causing the painted areas to be raised into relief. Not long after, it used to etch trajectory information plates for cannon and artillery operators, paper would rarely survive the rigors of combat. Often such information was etched onto equipment such as daggers or shovels. In 1782, the discovery was made by John Senebier that certain resins lost their solubility to turpentine when exposed to light, photo-chemical milling was extensively used in the development of photography methods, allowing light to create impressions on metal plates. Etching has applications in the circuit board and semiconductor fabrication industries. It is also used in the industry to remove shallow layers of material from large aircraft components, missile skin panels. Etching is used widely to manufacture integrated circuits and Microelectromechanical systems, in addition to the standard, liquid-based techniques, the semiconductor industry commonly uses plasma etching. Chemical milling is normally performed in a series of five steps, cleaning, masking, scribing, etching, cleaning is the preparatory process of ensuring that the surface to be etched is free of contaminants which could negatively impact the quality of the finished part. An improperly cleaned surface could result in poor adhesion of the maskant, causing areas to be etched erroneously, the surface must be kept free from oils, grease, primer coatings, markings and other residue from the marking out process, scale, and any other foreign contaminants. For most metals, this step can be performed by applying a solvent substance to the surface to be etched, the material may also be immersed in alkaline cleaners or specialized de-oxidizing solutions. It is common practice in modern industrial chemical etching facilities that the workpiece never be directly handled after this process, masking is the process of applying the maskant material to the surface to ensure that only desired areas are etched. Liquid maskants may be applied via dip-masking, in which the part is dipped into a tank of maskant. Maskant may also be applied by flow coating, liquid maskant is flowed over the surface of the part, certain conductive maskants may also be applied by electrostatic deposition, where electrical charges are applied to particles of maskant as it is sprayed onto the surface of the material
24.
Glass
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Glass is a non-crystalline amorphous solid that is often transparent and has widespread practical, technological, and decorative usage in, for example, window panes, tableware, and optoelectronics. The most familiar, and historically the oldest, types of glass are silicate glasses based on the chemical compound silica, the primary constituent of sand. The term glass, in usage, is often used to refer only to this type of material. Many applications of silicate glasses derive from their optical transparency, giving rise to their use as window panes. Glass can be coloured by adding metallic salts, and can also be painted and printed with vitreous enamels and these qualities have led to the extensive use of glass in the manufacture of art objects and in particular, stained glass windows. Although brittle, silicate glass is extremely durable, and many examples of glass fragments exist from early glass-making cultures, because glass can be formed or moulded into any shape, it has been traditionally used for vessels, bowls, vases, bottles, jars and drinking glasses. In its most solid forms it has also used for paperweights, marbles. Some objects historically were so commonly made of glass that they are simply called by the name of the material, such as drinking glasses. Porcelains and many polymer thermoplastics familiar from everyday use are glasses and these sorts of glasses can be made of quite different kinds of materials than silica, metallic alloys, ionic melts, aqueous solutions, molecular liquids, and polymers. For many applications, like glass bottles or eyewear, polymer glasses are a lighter alternative than traditional glass, silica is a common fundamental constituent of glass. In nature, vitrification of quartz occurs when lightning strikes sand, forming hollow, fused quartz is a glass made from chemically-pure SiO2. It has excellent resistance to shock, being able to survive immersion in water while red hot. However, its high melting-temperature and viscosity make it difficult to work with, normally, other substances are added to simplify processing. One is sodium carbonate, which lowers the transition temperature. The soda makes the glass water-soluble, which is undesirable, so lime, some magnesium oxide. The resulting glass contains about 70 to 74% silica by weight and is called a soda-lime glass, soda-lime glasses account for about 90% of manufactured glass. Most common glass contains other ingredients to change its properties, lead glass or flint glass is more brilliant because the increased refractive index causes noticeably more specular reflection and increased optical dispersion. Adding barium also increases the refractive index, iron can be incorporated into glass to absorb infrared energy, for example in heat absorbing filters for movie projectors, while cerium oxide can be used for glass that absorbs UV wavelengths
25.
External ballistics
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External ballistics or exterior ballistics is the part of ballistics that deals with the behavior of a projectile in flight. Gun-launched projectiles may be unpowered, deriving all their velocity from the propellants ignition until the exits the gun barrel. External ballistics is also concerned with the free-flight of other projectiles, such as balls, arrows etc. When in flight, the main or major forces acting on the projectile are gravity, drag, and if present, wind, if in powered fight, thrust, and if guided, the forces imparted by the control surfaces. In small arms external ballistics applications, gravity imparts a downward acceleration on the projectile, drag, or the air resistance, decelerates the projectile with a force proportional to the square of the velocity. Wind makes the projectile deviate from its trajectory, during flight, gravity, drag, and wind have a major impact on the path of the projectile, and must be accounted for when predicting how the projectile will travel. Meso variables can become significant for firearms users that have to deal with angled shot scenarios or extended ranges, at extremely long ranges, artillery must fire projectiles along trajectories that are not even approximately straight, they are closer to parabolic, although air resistance affects this. In super gun artillery cases, like the Paris gun, very subtle effects that are not covered in this article can further refine aiming solutions. The CP behind the CG condition yields stable projectile flight, meaning the projectile will not overturn during flight through the due to aerodynamic forces. Projectiles like small arms bullets and artillery shells must deal with their CP being in front of their CG, to stabilize such projectiles the projectile is spun around its longitudinal axis. The spinning mass creates gyroscopic forces that keep the bullets length axis resistant to the destabilizing overturning torque of the CP being in front of the CG, the effect of gravity on a projectile in flight is often referred to as projectile drop or bullet drop. It is important to understand the effect of gravity when zeroing the sighting components of a gun, to plan for projectile drop and compensate properly, one must understand parabolic shaped trajectories. In order for a projectile to impact any distant target, the barrel must be inclined to an elevation angle relative to the target. This is due to the fact that the projectile will begin to respond to the effects of gravity the instant it is free from the constraints of the bore. The imaginary line down the axis of the bore and out to infinity is called the line of departure and is the line on which the projectile leaves the barrel. Due to the effects of gravity a projectile can never impact a target higher than the line of departure, when a positively inclined projectile travels downrange, it arcs below the line of departure as it is being deflected off its initial path by gravity. Projectile/Bullet drop is defined as the distance of the projectile below the line of departure from the bore. Even when the line of departure is tilted upward or downward, projectile drop does not describe the actual trajectory of the projectile
26.
Optical fiber
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An optical fiber or optical fibre is a flexible, transparent fiber made by drawing glass or plastic to a diameter slightly thicker than that of a human hair. Fibers are also used for illumination, and are wrapped in bundles so that they may be used to carry images, thus allowing viewing in confined spaces, as in the case of a fiberscope. Specially designed fibers are used for a variety of other applications, some of them being fiber optic sensors. Optical fibers typically include a transparent core surrounded by a transparent cladding material with an index of refraction. Light is kept in the core by the phenomenon of internal reflection which causes the fiber to act as a waveguide. Fibers that support many propagation paths or transverse modes are called multi-mode fibers, multi-mode fibers generally have a wider core diameter and are used for short-distance communication links and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 1,000 meters, being able to join optical fibers with low loss is important in fiber optic communication. This is more complex than joining electrical wire or cable and involves careful cleaving of the fibers, precise alignment of the cores. For applications that demand a permanent connection a fusion splice is common, in this technique, an electric arc is used to melt the ends of the fibers together. Another common technique is a splice, where the ends of the fibers are held in contact by mechanical force. Temporary or semi-permanent connections are made by means of specialized optical fiber connectors, the field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics. The term was coined by Indian physicist Narinder Singh Kapany who is acknowledged as the father of fiber optics. Guiding of light by refraction, the principle that makes fiber optics possible, was first demonstrated by Daniel Colladon, John Tyndall included a demonstration of it in his public lectures in London,12 years later. When the ray passes from water to air it is bent from the perpendicular. If the angle which the ray in water encloses with the perpendicular to the surface be greater than 48 degrees, the angle which marks the limit where total reflection begins is called the limiting angle of the medium. For water this angle is 48°27′, for flint glass it is 38°41′, unpigmented human hairs have also been shown to act as an optical fiber. Practical applications, such as close internal illumination during dentistry, appeared early in the twentieth century, image transmission through tubes was demonstrated independently by the radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the 1920s. The principle was first used for medical examinations by Heinrich Lamm in the following decade
27.
Light tube
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Light tubes or light pipes are physical structures used for transporting or distributing natural or artificial light for the purpose of illumination, and are examples of optical waveguides. In their application to daylighting, they are often called tubular daylighting devices, sun pipes, sun scopes. Light pipes may be divided into two categories, hollow structures that contain the light with a reflective lining, and transparent solids that contain the light by total internal reflection. The principles governing the flow of light through these devices are those of nonimaging optics, both have the purpose of lighting, for example in architecture. Manufacturing custom designed Infrared light pipes, hollow waveguides and homogenizers is non-trivial, laser Black can be applied to certain parts of light pipes to absorb IR light. This is done to limit IR light to certain areas of the pipe. While most light pipes are produced with a round cross-section, light pipes are not limited to this geometry, square and hexagonal cross-sections are used in special applications. Hexagonal pipes tend to produce the most homogenized type of IR Light, the pipes do not need to be straight. Bends in the pipe have little effect on efficiency, also known as a “tubular skylight” or “tubular daylighting device”, this is the oldest and most widespread type of light tube used for daylighting. The concept was developed by the ancient Egyptians. The first commercial systems were patented and marketed in the 1850s by Paul Emile Chappuis in London. Chappuis Ltd’s reflectors were in production until the factory was destroyed in 1943. The concept was rediscovered and patented in 1986 by Solatube International of Australia and this system has been marketed for widespread residential and commercial use. Other daylighting products are on the market under various names, such as “SunScope”, “solar pipe”, “light pipe”, “light tube”. A tube lined with highly reflective material leads the light rays through a building, starting from an entrance-point located on its roof or one of its outer walls. A light tube is not intended for imaging, thus image distortions pose no problem and are in many ways encouraged due to the reduction of “directional” light. The entrance point usually comprises a dome, which has the function of collecting and reflecting as much sunlight as possible into the tube, many units also have directional “collectors”, “reflectors” or even Fresnel lens devices that assist in collecting additional directional light down the tube. In 2003, Veronica Garcia Hansen, Ken Yeang, and Ian Edmonds were awarded the Far East Economic Review Innovation Award in bronze for this development, Light transmission efficiency is greatest if the tube is short and straight
28.
Battery (electricity)
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An electric battery is a device consisting of one or more electrochemical cells with external connections provided to power electrical devices such as flashlights, smartphones, and electric cars. When a battery is supplying power, its positive terminal is the cathode. The terminal marked negative is the source of electrons that when connected to a circuit will flow. It is the movement of ions within the battery which allows current to flow out of the battery to perform work. Historically the term specifically referred to a device composed of multiple cells. Primary batteries are used once and discarded, the materials are irreversibly changed during discharge. Common examples are the battery used for flashlights and a multitude of portable electronic devices. Secondary batteries can be discharged and recharged multiple times using mains power from a wall socket, examples include the lead-acid batteries used in vehicles and lithium-ion batteries used for portable electronics such as laptops and smartphones. According to a 2005 estimate, the battery industry generates US$48 billion in sales each year. Batteries have much lower energy than common fuels such as gasoline. This is somewhat offset by the efficiency of electric motors in producing mechanical work. The usage of battery to describe a group of electrical devices dates to Benjamin Franklin, alessandro Volta built and described the first electrochemical battery, the voltaic pile, in 1800. This was a stack of copper and zinc plates, separated by brine-soaked paper disks, Volta did not understand that the voltage was due to chemical reactions. Although early batteries were of value for experimental purposes, in practice their voltages fluctuated. It consisted of a pot filled with a copper sulfate solution, in which was immersed an unglazed earthenware container filled with sulfuric acid. These wet cells used liquid electrolytes, which were prone to leakage and spillage if not handled correctly, many used glass jars to hold their components, which made them fragile and potentially dangerous. These characteristics made wet cells unsuitable for portable appliances, near the end of the nineteenth century, the invention of dry cell batteries, which replaced the liquid electrolyte with a paste, made portable electrical devices practical. Batteries convert chemical energy directly to electrical energy, a battery consists of some number of voltaic cells
29.
LED
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A light-emitting diode is a two-lead semiconductor light source. It is a p–n junction diode, which emits light when activated, when a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence, and the color of the light is determined by the band gap of the semiconductor. LEDs are typically small and integrated optical components may be used to shape the radiation pattern, appearing as practical electronic components in 1962, the earliest LEDs emitted low-intensity infrared light. Infrared LEDs are still used as transmitting elements in remote-control circuits. The first visible-light LEDs were also of low intensity and limited to red, modern LEDs are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness. Early LEDs were often used as indicator lamps for electronic devices and they were soon packaged into numeric readouts in the form of seven-segment displays and were commonly seen in digital clocks. Recent developments in LEDs permit them to be used in environmental, LEDs have allowed new displays and sensors to be developed, while their high switching rates are also used in advanced communications technology. LEDs have many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching. Light-emitting diodes are now used in applications as diverse as aviation lighting, automotive headlamps, advertising, general lighting, traffic signals, camera flashes, as of 2017, LED lights home room lighting are as cheap or cheaper than compact fluorescent lamp sources of comparable output. They are also more energy efficient and, arguably, have fewer environmental concerns linked to their disposal. Electroluminescence as a phenomenon was discovered in 1907 by the British experimenter H. J. Round of Marconi Labs, using a crystal of silicon carbide, russian inventor Oleg Losev reported creation of the first LED in 1927. His research was distributed in Soviet, German and British scientific journals, rubin Braunstein of the Radio Corporation of America reported on infrared emission from gallium arsenide and other semiconductor alloys in 1955. Braunstein observed infrared emission generated by simple diode structures using gallium antimonide, GaAs, indium phosphide, in 1957, Braunstein further demonstrated that the rudimentary devices could be used for non-radio communication across a short distance. As noted by Kroemer Braunstein …had set up a simple optical communications link, the emitted light was detected by a PbS diode some distance away. This signal was fed into an amplifier and played back by a loudspeaker. Intercepting the beam stopped the music and we had a great deal of fun playing with this setup. This setup presaged the use of LEDs for optical communication applications, by October 1961, they had demonstrated efficient light emission and signal coupling between a GaAs p-n junction light emitter and an electrically-isolated semiconductor photodetector
30.
Tritium
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Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons, naturally occurring tritium is extremely rare on Earth, where trace amounts are formed by the interaction of the atmosphere with cosmic rays. It can be produced by irradiating lithium metal or lithium bearing ceramic pebbles in a nuclear reactor, the name of this isotope is derived from the Greek word τρίτος meaning third. While tritium has several different experimentally determined values of its half-life and it decays into helium-3 by beta decay as in this nuclear equation, and it releases 18.6 keV of energy in the process. The electrons kinetic energy varies, with an average of 5.7 keV, beta particles from tritium can penetrate only about 6.0 mm of air, and they are incapable of passing through the dead outermost layer of human skin. The unusually low energy released in the beta decay makes the decay appropriate for absolute neutrino mass measurements in the laboratory. The low energy of tritiums radiation makes it difficult to detect tritium-labeled compounds except by using liquid scintillation counting, Tritium is produced in nuclear reactors by neutron activation of lithium-6. This is possible with neutrons of any energy, and is an exothermic reaction yielding 4.8 MeV, in comparison, the fusion of deuterium with tritium releases about 17.6 MeV of energy. High-energy neutrons can produce tritium from lithium-7 in an endothermic reaction. This was discovered when the 1954 Castle Bravo nuclear test produced a high yield. High-energy neutrons irradiating boron-10 will also produce tritium, A more common result of boron-10 neutron capture is 7Li. The reactions requiring high neutron energies are not attractive production methods for peaceful applications, Tritium is also produced in heavy water-moderated reactors whenever a deuterium nucleus captures a neutron. This reaction has a quite small absorption cross section, making water a good neutron moderator. Even so, cleaning tritium from the moderator may be desirable after several years to reduce the risk of its escaping to the environment. Ontario Power Generations Tritium Removal Facility processes up to 2,500 tonnes of water a year. Deuteriums absorption cross section for thermal neutrons is about 0.52 millibarns, whereas that of oxygen-16 is about 0.19 millibarns and that of oxygen-17 is about 240 millibarns. Tritium is a product of the nuclear fission of uranium-235, plutonium-239. The release or recovery of tritium needs to be considered in the operation of reactors, especially in the reprocessing of nuclear fuels
31.
SA80
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The SA80 is a British family of 5. 56×45mm NATO small arms. It is a fire, gas-operated assault rifle. Mechanically, it has derived from the Armalite AR-18, which had been manufactured under licence in the UK by Sterling Armaments Company. The first prototypes were tried in 1976, and production ended in 1994 and it is due to remain in service until 2025. The L85 rifle variant of the SA80 family has been the issue service rifle of the British Armed Forces since 1987. The A1 variant was upgraded in the early 2000s by Heckler & Koch as the SA80A2, in mid-2016 a prototype A3 variant was showcased which further improved on the weapon and is reportedly being considered to extend the out of service date beyond 2025. The remainder of the family comprises the L86 Light Support Weapon, the short-barrelled L22 carbine, the SA80 was the last in a long line of British weapons to come from the Royal Small Arms Factory, the national arms development and production facility at Enfield Lock. Two 7mm prototypes were built in a configuration, designated the EM-1. When NATO adopted the 7. 62×51mm NATO rifle cartridge as the standard calibre for its service rifles, in 1969, the Enfield factory began work on a brand new family of weapons, chambered in a newly designed British 4. 85×49mm intermediate cartridge. The system was to be composed of two weapons, the XL64E5 rifle and a support weapon known as the XL65E4 light machine gun. During the development of the SA-80 a bullpup conversion was made of an AR-18 and a Stoner 63 at Enfield. Technically, in the mid-1970s, the 4. 85×49mm round was seen as superior to the existing version of 5. 56mm M193 round in use by the US. For the 4.85 mm round, both propellant and projectile were at the beginning of their respective development curves, also, weight for weight, more rounds of ammunition could be carried by an individual soldier – a considerable advantage on the battlefield. It was regarded as probable at the time that the argument for the 5.56 mm standard within NATO had more to do with the economics involved, over the lifetime of a small-arms weapon type, far more money is spent on the munitions than the weapons themselves. In 1976, the prototypes were ready to undergo trials, however, after NATOs decision to standardise ammunition among its members, Enfield engineers re-chambered the rifles to the American 5. 56×45mm NATO M193 cartridge. The newly redesigned 5.56 mm version of the XL64E5 became known as the XL70E3, the left-handed XL68 was also re-chambered in 5. 56×45mm as the XL78. The 5. 56mm light support variant, the XL73E3. Further development out of the initial so-called Phase A pre-production series led to the XL85, while the XL85E1 and XL86E1 were ultimately adopted as the L85 and L86 respectively, a number of additional test models were produced
32.
Advanced Combat Optical Gunsight
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Advanced Combat Optical Gunsights are a series of telescopic sights manufactured by Trijicon. The ACOG was originally designed to be used on the M16 rifle and M4 carbine, models provide fixed power magnification levels from 1. 5× to 6×. ACOG reticles are illuminated at night by an internal phosphor, some versions have an additional daytime reticle illumination via a passive external fiber optic light pipe or are LED-illuminated using a battery. The ACOG is available in a variety of configurations from the manufacturer with different reticles, illumination, most ACOGs do not use batteries for reticle illumination, being designed to use internal phosphor illumination provided by the radioactive decay of tritium. The tritium illumination has a life of 10–15 years. Some versions of the ACOG have an additional daytime reticle illumination via a passive external fiber optic light pipe, reticles have other features such as a bullet drop compensator and other different reticle shapes such as chevrons. Some ACOG models incorporate rudimentary ghost ring iron sights as a backup for targets that are within 50 m, most ACOG models, when mounted to a carry handle, have an open space through the mount to allow the use of the rifles iron sights without removing the scope. Others include Docter or Trijicon reflex sights mounted on top, the ACOG ECOS line features both of these secondary sighting systems on the same scope. Other features include Picatinny rails, flip caps, and the ability to be waterproof up to 11 m, although the ACOG is designed for the Picatinny rail of the M16A4 and M4, it can be mounted on the carrying handles of previous models by using a special adapter. Several ACOG models are designed to be used with the Bindon Aiming Concept, the technique is essentially using the illuminated part of the reticle and its focusing rear eyepiece as a collimator sight. In this both-eyes-open technique the brain superimposes the aiming reticle on the target, an added part of the technique is to shift focus after acquisition to the dominant eye/telescopic image for more accurate shooting. This overcomes the problem of centering or acquiring fast traversing targets common with all telescopic sights, only certain models of the ACOG are designed with bright enough daylight-lit fiber optic or battery-powered LED reticles that facilitate this technique. Greece, Hellenic Army Commandos and SFs United Kingdom, British Army, United States, United States armed forces, various law enforcement agencies. This sight is designated the M150 Rifle Combat Optic in Army service, after an October 2005 evaluation, the USMC fielded 115,000 ACOGs so that every rifle and every carbine in the Marine Corps inventory would be equipped with one. Other Trijicon models have seen service after being purchased at the unit. Trijicon has been the subject of criticism for inscribing a reference to a Bible verse alongside the model numbers on their ACOG sights. Starting in late 2009, Trijicon began shipping sights to the U. S. military without the Bible verse, sight SUSAT, 4× telescopic sight with tritium-powered illumination similar to the ACOG Article on the Trijicon ACOG An italian article about TA44S
33.
Night vision
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Night vision is the ability to see in low light conditions. Whether by biological or technological means, night vision is possible by a combination of two approaches, sufficient spectral range, and sufficient intensity range. Humans have poor night vision compared to animals, in part because the human eye lacks a tapetum lucidum. Night-useful spectral range techniques can sense radiation that is invisible to a human observer, human vision is confined to a small portion of the electromagnetic spectrum called visible light. Enhanced spectral range allows the viewer to take advantage of sources of electromagnetic radiation. Some animals such as the shrimp can see using much more of the infrared and/or ultraviolet spectrum than humans. Sufficient intensity range is simply the ability to see with very small quantities of light, many animals have better night vision than humans do, the result of one or more differences in the morphology and anatomy of their eyes. These include having a larger eyeball, a lens, a larger optical aperture, more rods than cones in the retina. Enhanced intensity range is achieved via technological means through the use of an image intensifier, gain multiplication CCD, or other very low-noise and high-sensitivity array of photodetectors. All photoreceptor cells in the eye contain molecules of photoreceptor protein which is a combination of the protein photopsin in color vision cells, rhodopsin in night vision cells, and retinal. The retinal must diffuse from the cell, out of the eye. In bright light conditions, most of the retinal is not in the photoreceptors and it takes about 45 minutes of dark for all of the photoreceptor proteins to be recharged with active retinal, but most of the night vision adaptation occurs within the first five minutes in the dark. Adaptation results in sensitivity to light. In dark conditions only the rod cells have enough sensitivity to respond, rhodopsin in the human rods is insensitive to the longer red wavelengths, so traditionally many people use red light to help preserve night vision. Red light only slowly depletes the rhodopsin stores in the rods, another theory posits that since stars typically emit light with shorter wavelengths, the light from stars will be in the blue-green color spectrum. Therefore, using red light to navigate would not desensitize the receptors used to detect star light, using red light for night vision is less effective for people with red–green color blindness, due to their insensitivity to red light. This is found in nocturnal animals and some deep sea animals. Humans, and monkeys, lack a tapetum lucidum, nocturnal mammals have rods with unique properties that make enhanced night vision possible
34.
Virtual image
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In optics, a virtual image is an image formed when the outgoing rays from a point on an object always diverge. The image appears to be located at the point of apparent divergence, because the rays never really converge, a virtual image cannot be projected onto a screen. In diagrams of systems, virtual rays are conventionally represented by dotted lines. Virtual images are located by tracing the rays that emerge from an optical device backward to a perceived point of origin. In contrast, an image is one that is formed when the outgoing rays forms a point converging at a real location. Real images can be projected onto a diffuse reflecting screen, but a screen is not necessary for the image to form, a plane mirror forms a virtual image positioned behind the mirror. Although the rays of light seem to come from behind the mirror, the image in a plane mirror is not magnified and appears to be as far behind the mirror as the object is in front of the mirror. A diverging lens or a convex mirror forms a virtual image, such an image is reduced in size when compared to the original object. A converging lens or a mirror is also capable of producing a virtual image if the object is within the focal length. Such an image will be magnified, in contrast, an object placed in front of a converging lens or concave mirror at a position beyond the focal length produces a real image. Such an image may be magnified or reduced depending on the position of the object
35.
Collimator sight
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A collimator sight is a type of optical sight that allows the user looking into it to see an illuminated aiming point aligned with the device the sight is attached-to regardless of eye position. Collimator sights are an old idea, being used in many forms for almost 100 years. They are also referred to as collimating sights or occluded eye gunsight, the basic layout of a collimator sight is a closed tube with a lens at its open end and a luminous reticle mounted near the closed end at the focus of the lens, creating an optical collimator. The reticle is illuminated by a light source or by ambient light gathered behind the reticle via an opalescent window or fiber optic light pipe. Collimator sights as weapon sights are considered to be simple, rugged. They have been used on mortars and field guns since World War I, there have had more modern incarnations such as the Armson Occluded Eye Gunsight and the Normark Corp. These both used a light gathering rod in a clear dome collecting ambient light to illuminate a dot style reticle. Glossary of military abbreviations Reflector sight Elementary optics and applications to fire control instruments, ordnance Dept, page 82, THE COLLIMATOR
36.
Refraction
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Refraction is the change in direction of wave propagation due to a change in its transmission medium. The phenomenon is explained by the conservation of energy and the conservation of momentum, due to the change of medium, the phase velocity of the wave is changed but its frequency remains constant. This is most commonly observed when a wave passes from one medium to another at any other than 0° from the normal. In optics, refraction is a phenomenon that occurs when waves travel from a medium with a given refractive index to a medium with another at an oblique angle. At the boundary between the media, the phase velocity is altered, usually causing a change in direction. Its wavelength increases or decreases, but its frequency remains constant, for example, a light ray will refract as it enters and leaves glass, assuming there is a change in refractive index. A ray traveling along the normal will change speed, but not direction, refraction still occurs in this case. Understanding of this led to the invention of lenses and the refracting telescope. Refraction can be seen looking into a bowl of water. Air has a index of about 1.0003. If a person looks at an object, such as a pencil or straw, which is placed at a slant, partially in the water. This is due to the bending of light rays as they move from the water to the air, once the rays reach the eye, the eye traces them back as straight lines. The lines of sight intersect at a position than where the actual rays originated. This causes the pencil to appear higher and the water to appear shallower than it really is, the depth that the water appears to be when viewed from above is known as the apparent depth. This is an important consideration for spearfishing from the surface because it will make the fish appear to be in a different place. Conversely, an object above the water has a higher apparent height when viewed from below the water, the opposite correction must be made by an archer fish. For small angles of incidence, the ratio of apparent to real depth is the ratio of the indexes of air to that of water. But, as the angle of incidence approaches 90o, the apparent depth approaches zero, albeit reflection increases, the diagram on the right shows an example of refraction in water waves
37.
Reflection (physics)
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Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves, the law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. In acoustics, reflection causes echoes and is used in sonar, in geology, it is important in the study of seismic waves. Reflection is observed with surface waves in bodies of water, Reflection is observed with many types of electromagnetic wave, besides visible light. Reflection of VHF and higher frequencies is important for radio transmission, even hard X-rays and gamma rays can be reflected at shallow angles with special grazing mirrors. Reflection of light is either specular or diffuse depending on the nature of the interface, a mirror provides the most common model for specular light reflection, and typically consists of a glass sheet with a metallic coating where the reflection actually occurs. Reflection is enhanced in metals by suppression of wave propagation beyond their skin depths, Reflection also occurs at the surface of transparent media, such as water or glass. In the diagram, a light ray PO strikes a vertical mirror at point O, by projecting an imaginary line through point O perpendicular to the mirror, known as the normal, we can measure the angle of incidence, θi and the angle of reflection, θr. The law of reflection states that θi = θr, or in other words, in fact, reflection of light may occur whenever light travels from a medium of a given refractive index into a medium with a different refractive index. In the most general case, a fraction of the light is reflected from the interface. This is analogous to the way impedance mismatch in a circuit causes reflection of signals. Total internal reflection of light from a denser medium occurs if the angle of incidence is above the critical angle, total internal reflection is used as a means of focusing waves that cannot effectively be reflected by common means. X-ray telescopes are constructed by creating a tunnel for the waves. As the waves interact at low angle with the surface of this tunnel they are reflected toward the focus point, a conventional reflector would be useless as the X-rays would simply pass through the intended reflector. When light reflects off a material denser than the external medium, in contrast, a less dense, lower refractive index material will reflect light in phase. This is an important principle in the field of thin-film optics, specular reflection at a curved surface forms an image which may be magnified or demagnified, curved mirrors have optical power. Such mirrors may have surfaces that are spherical or parabolic, if the reflecting surface is very smooth, the reflection of light that occurs is called specular or regular reflection. The laws of reflection are as follows, The incident ray, the reflected ray, the angle which the incident ray makes with the normal is equal to the angle which the reflected ray makes to the same normal
38.
Collimator
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A collimator is a device that narrows a beam of particles or waves. To narrow can mean either to cause the directions of motion to become aligned in a specific direction. An English physicist Henry Kater was the inventor of the floating collimator and he reported about his invention in January 1825. In his report, Kater mentioned previous work in area by Carl Friedrich Gauss. In optics, a collimator may consist of a mirror or lens with some type of light source and/or an image at its focus. This can be used to replicate a target focused at infinity with little or no parallax, in lighting, collimators are typically designed using the principles of nonimaging optics. A surveying camera may be collimated by setting its fiduciary markers so that they define the principal point, optical collimators are also used as gun sights in the collimator sight, which is a simple optical collimator with a cross hair or some other reticle at its focus. The viewer only sees an image of the reticle, adding a beam splitter allows the viewer to see the reticle and the field of view, making a reflector sight. Collimators may be used with laser diodes and CO2 cutting lasers, proper collimation of a laser source with long enough coherence length can be verified with a shearing interferometer. In neutron, X-ray, and gamma ray optics, a collimator is a device that filters a stream of rays so that only those traveling parallel to a direction are allowed through. Collimators are also used with radiation detectors in nuclear power stations for monitoring sources of radioactivity, the figure to the right illustrates how a Söller collimator is used in neutron and X-ray machines. The upper panel shows a situation where a collimator is not used, in both panels the source of radiation is to the right, and the image is recorded on the gray plate at the left of the panels. The resultant image will be so blurred and indistinct as to be useless, in the lower panel of the figure, a collimator has been added. This can be something simple e. g. air, or if mechanical strength is needed then aluminium may be used. If this forms part of an assembly, the sandwich may be curved. This allows energy selection in addition to collimation - the curvature of the collimator, only rays that are travelling nearly parallel to the holes will pass through them—any others will be absorbed by hitting the plate surface or the side of a hole. This ensures that rays are recorded in their place on the plate. A collimator in this instance is most commonly made of tungsten, for instance, the thinnest walls on the sides of a 4 HVL tungsten collimator 13 mm thick will reduce the intensity of radiation passing through them by 88. 5%
39.
Collimated light
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Collimated light is light whose rays are parallel, and therefore will spread minimally as it propagates. A perfectly collimated beam, with no divergence, would not disperse with distance, such a beam cannot be created, due to diffraction. Light can be collimated by a number of processes, for instance by means of a collimator. Perfectly collimated light is said to be focused at infinity. Thus, as the distance from a point source increases, the spherical wavefronts become flatter and closer to plane waves, the word collimate comes from the Latin verb collimare, which originated in a misreading of collineare, to direct in a straight line. In practice, gas lasers can use concave mirrors, flat mirrors, the divergence of high-quality laser beams is commonly less than 1 milliradian, and can be much less for large-diameter beams. Laser diodes emit less-collimated light due to their short cavity, synchrotron light is very well collimated. It is produced by bending relativistic electrons around a circular track, when the electrons are at relativistic speeds, the resulting radiation is highly collimated, a result which does not occur at slower speeds. The light from stars can be considered collimated for almost any purpose, because they are so far away they have almost no angular size, light from the Sun is nearly collimated by the time it reaches Earth because of its distance from the Earth. A perfect parabolic mirror will bring parallel rays to a focus at a single point, conversely, a point source at the focus of a parabolic mirror will produce a beam of collimated light creating a Collimator. Since the source needs to be small, such a system cannot produce much optical power. Spherical mirrors are easier to make than parabolic mirrors and they are used to produce approximately collimated light. Many types of lenses can also produce collimated light from point-like sources and this principle is used in full flight simulators, that have specially designed systems for displaying imagery of the Out-The-Window scene to the pilots in the replica aircraft cabin. Collimation refers to all the elements in an instrument being on their designed optical axis. It also refers to the process of adjusting an optical instrument so that all its elements are on that designed axis. With regards to a telescope, the term refers to the fact that the axis of each optical component should be centered and parallel. Most amateur reflector telescopes need to be re-collimated every few years to maintain optimum performance, collimation can also be tested using a shearing interferometer, which is often used to test laser collimation. Decollimation is any mechanism or process which causes a beam with the minimum possible ray divergence to diverge or converge from parallelism, decollimation must be accounted for to fully treat many systems such as radio, radar, sonar, and optical communications
40.
Sight (device)
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A sight is a device used to assist aligning or aim weapons, surveying instruments, or other items by eye. Sights can be a set or system of markers that have to be aligned together as well as aligned with the target. They can also be optical devices that allow the user to see the image of an aiming point in the same focus as the target. These include telescopic sights and reflector sights, There are also sights that project an aiming point onto the target itself, such as laser sights. At its simplest, a sight typically has two components, front and rear aiming pieces that have to be lined up, sights such as this can be found on many types of devices including weapons, surveying and measuring instruments, and navigational tools. On weapons, these sights are usually formed by rugged metal parts, giving them the iron sights. On many types of weapons they are built-in and may be fixed, adjustable, or marked for elevation, windage, target speed and they are also classified in forms of notch or aperture. Optical sights use optics that give the user an image of an aiming point or pattern superimposed at the same focus as the target. Telescopic sights are used on a range of devices including guns, surveying equipment. These sights have been around for over 100 years and been used on all types of weapons, reflector sights were first used as a weapon sight in German aircraft towards the end of World War I. Collimator sight Holographic weapon sight There are many types of sighting devices and they can be fixed, mechanical, optical, computational, or a mixture of all of these attributes
41.
Laser
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A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term laser originated as an acronym for light amplification by stimulated emission of radiation, the first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light coherently, spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances, Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum, i. e. they can emit a single color of light. Temporal coherence can be used to produce pulses of light as short as a femtosecond, Lasers are distinguished from other light sources by their coherence. Spatial coherence is typically expressed through the output being a narrow beam, Laser beams can be focused to very tiny spots, achieving a very high irradiance, or they can have very low divergence in order to concentrate their power at a great distance. Temporal coherence implies a polarized wave at a single frequency whose phase is correlated over a great distance along the beam. A beam produced by a thermal or other incoherent light source has an amplitude and phase that vary randomly with respect to time and position. Lasers are characterized according to their wavelength in a vacuum, most single wavelength lasers actually produce radiation in several modes having slightly differing frequencies, often not in a single polarization. Although temporal coherence implies monochromaticity, there are lasers that emit a broad spectrum of light or emit different wavelengths of light simultaneously, there are some lasers that are not single spatial mode and consequently have light beams that diverge more than is required by the diffraction limit. However, all devices are classified as lasers based on their method of producing light. Lasers are employed in applications where light of the spatial or temporal coherence could not be produced using simpler technologies. The word laser started as an acronym for light amplification by stimulated emission of radiation, in the early technical literature, especially at Bell Telephone Laboratories, the laser was called an optical maser, this term is now obsolete. A laser that produces light by itself is technically an optical rather than an optical amplifier as suggested by the acronym. It has been noted that the acronym LOSER, for light oscillation by stimulated emission of radiation. With the widespread use of the acronym as a common noun, optical amplifiers have come to be referred to as laser amplifiers. The back-formed verb to lase is frequently used in the field, meaning to produce light, especially in reference to the gain medium of a laser. Further use of the laser and maser in an extended sense, not referring to laser technology or devices, can be seen in usages such as astrophysical maser
42.
Radar
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Radar is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, Radio waves from the transmitter reflect off the object and return to the receiver, giving information about the objects location and speed. Radar was developed secretly for military use by several nations in the period before, the term RADAR was coined in 1940 by the United States Navy as an acronym for RAdio Detection And Ranging or RAdio Direction And Ranging. The term radar has since entered English and other languages as a common noun, high tech radar systems are associated with digital signal processing, machine learning and are capable of extracting useful information from very high noise levels. Other systems similar to make use of other parts of the electromagnetic spectrum. One example is lidar, which uses ultraviolet, visible, or near infrared light from lasers rather than radio waves, as early as 1886, German physicist Heinrich Hertz showed that radio waves could be reflected from solid objects. In 1895, Alexander Popov, an instructor at the Imperial Russian Navy school in Kronstadt. The next year, he added a spark-gap transmitter, in 1897, while testing this equipment for communicating between two ships in the Baltic Sea, he took note of an interference beat caused by the passage of a third vessel. In his report, Popov wrote that this phenomenon might be used for detecting objects, the German inventor Christian Hülsmeyer was the first to use radio waves to detect the presence of distant metallic objects. In 1904, he demonstrated the feasibility of detecting a ship in dense fog and he obtained a patent for his detection device in April 1904 and later a patent for a related amendment for estimating the distance to the ship. He also got a British patent on September 23,1904 for a radar system. It operated on a 50 cm wavelength and the radar signal was created via a spark-gap. In 1915, Robert Watson-Watt used radio technology to advance warning to airmen. Watson-Watt became an expert on the use of direction finding as part of his lightning experiments. As part of ongoing experiments, he asked the new boy, Arnold Frederic Wilkins, Wilkins made an extensive study of available units before selecting a receiver model from the General Post Office. Its instruction manual noted that there was fading when aircraft flew by, in 1922, A. Hoyt Taylor and Leo C. Taylor submitted a report, suggesting that this might be used to detect the presence of ships in low visibility, eight years later, Lawrence A. Australia, Canada, New Zealand, and South Africa followed prewar Great Britain, and Hungary had similar developments during the war. Hugon, began developing a radio apparatus, a part of which was installed on the liner Normandie in 1935
43.
Computer
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A computer is a device that can be instructed to carry out an arbitrary set of arithmetic or logical operations automatically. The ability of computers to follow a sequence of operations, called a program, such computers are used as control systems for a very wide variety of industrial and consumer devices. The Internet is run on computers and it millions of other computers. Since ancient times, simple manual devices like the abacus aided people in doing calculations, early in the Industrial Revolution, some mechanical devices were built to automate long tedious tasks, such as guiding patterns for looms. More sophisticated electrical machines did specialized analog calculations in the early 20th century, the first digital electronic calculating machines were developed during World War II. The speed, power, and versatility of computers has increased continuously and dramatically since then, conventionally, a modern computer consists of at least one processing element, typically a central processing unit, and some form of memory. The processing element carries out arithmetic and logical operations, and a sequencing, peripheral devices include input devices, output devices, and input/output devices that perform both functions. Peripheral devices allow information to be retrieved from an external source and this usage of the term referred to a person who carried out calculations or computations. The word continued with the same meaning until the middle of the 20th century, from the end of the 19th century the word began to take on its more familiar meaning, a machine that carries out computations. The Online Etymology Dictionary gives the first attested use of computer in the 1640s, one who calculates, the Online Etymology Dictionary states that the use of the term to mean calculating machine is from 1897. The Online Etymology Dictionary indicates that the use of the term. 1945 under this name, theoretical from 1937, as Turing machine, devices have been used to aid computation for thousands of years, mostly using one-to-one correspondence with fingers. The earliest counting device was probably a form of tally stick, later record keeping aids throughout the Fertile Crescent included calculi which represented counts of items, probably livestock or grains, sealed in hollow unbaked clay containers. The use of counting rods is one example, the abacus was initially used for arithmetic tasks. The Roman abacus was developed from used in Babylonia as early as 2400 BC. Since then, many forms of reckoning boards or tables have been invented. In a medieval European counting house, a checkered cloth would be placed on a table, the Antikythera mechanism is believed to be the earliest mechanical analog computer, according to Derek J. de Solla Price. It was designed to calculate astronomical positions and it was discovered in 1901 in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete, and has been dated to circa 100 BC
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Light-emitting diode
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A light-emitting diode is a two-lead semiconductor light source. It is a p–n junction diode, which emits light when activated, when a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence, and the color of the light is determined by the band gap of the semiconductor. LEDs are typically small and integrated optical components may be used to shape the radiation pattern, appearing as practical electronic components in 1962, the earliest LEDs emitted low-intensity infrared light. Infrared LEDs are still used as transmitting elements in remote-control circuits. The first visible-light LEDs were also of low intensity and limited to red, modern LEDs are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness. Early LEDs were often used as indicator lamps for electronic devices and they were soon packaged into numeric readouts in the form of seven-segment displays and were commonly seen in digital clocks. Recent developments in LEDs permit them to be used in environmental, LEDs have allowed new displays and sensors to be developed, while their high switching rates are also used in advanced communications technology. LEDs have many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching. Light-emitting diodes are now used in applications as diverse as aviation lighting, automotive headlamps, advertising, general lighting, traffic signals, camera flashes, as of 2017, LED lights home room lighting are as cheap or cheaper than compact fluorescent lamp sources of comparable output. They are also more energy efficient and, arguably, have fewer environmental concerns linked to their disposal. Electroluminescence as a phenomenon was discovered in 1907 by the British experimenter H. J. Round of Marconi Labs, using a crystal of silicon carbide, russian inventor Oleg Losev reported creation of the first LED in 1927. His research was distributed in Soviet, German and British scientific journals, rubin Braunstein of the Radio Corporation of America reported on infrared emission from gallium arsenide and other semiconductor alloys in 1955. Braunstein observed infrared emission generated by simple diode structures using gallium antimonide, GaAs, indium phosphide, in 1957, Braunstein further demonstrated that the rudimentary devices could be used for non-radio communication across a short distance. As noted by Kroemer Braunstein …had set up a simple optical communications link, the emitted light was detected by a PbS diode some distance away. This signal was fed into an amplifier and played back by a loudspeaker. Intercepting the beam stopped the music and we had a great deal of fun playing with this setup. This setup presaged the use of LEDs for optical communication applications, by October 1961, they had demonstrated efficient light emission and signal coupling between a GaAs p-n junction light emitter and an electrically-isolated semiconductor photodetector
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Red dot sight
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They are considered to be fast acquisition and easy to use gun sights for target shooting, hunting, and in police and military applications. Aside from firearm applications, they are used on cameras. On cameras they are used to flying aircraft, birds in flight. Telescopes have a field of view and therefore are often equipped with a secondary finder scope such as a red dot sight. The typical configuration for a red dot sight is a spherical mirror reflector with a red light-emitting diode at its off axis focus. The mirror has a partially silvered multilayer dielectric dichroic coating designed to reflect just the red spectrum allowing it to pass through most other light, the size of the dot generated by the LED is controlled by an aperture hole in front of it made from metal or coated glass. The LED as a reticle is an innovation that improves the reliability. There is no need for other elements to focus light behind a reticle. And the LED itself is solid state and consumes little power, allowing battery powered sights to run for hundreds. Using a dot shaped reticle also greatly simplifies the sight since the small diameter image does not require a sophisticated optical reflector to focus it, more complex reticle patterns such as cross hairs or concentric circles can be used but need more complex aberration free optics. This is compensated for by keeping the dot in the middle of the optical window, some manufacturers modify the focus of the LED/optical collimator combination, making models with the optical collimator set to focus the dot at a finite distance. These have an amount of parallax due to eye movement, equal to the size of the optical window, at close range. Red dot sights generally fall into two categories, tube or open designs, tube sights look similar to a standard telescopic sight, with a cylindrical tube containing the optics. Tube sights offer the option of fitted dust covers and the ability to add filters, such as polarizing or haze filters, since a reflector sight only really needs a single optical surface, the reflector, the tube is not needed. This allows for non-tubed open sights that consist of a flat base, the idea of attaching a reflector sight to a firearm has been around since the sights invention in 1900. Many different types of reflector sights designed for firearms have been marketed over the past half century, some lit by batteries. One, the Weaver Qwik-Point, even presented the viewer with a red aiming dot due to the red plastic light pipe used to collect ambient light, the sight was called the Aimpoint Electronic and had a closed tube design that could be mounted similar to a telescopic sight. The LED could run for 1500 to 3000 hours on mercury batteries, other manufacturers soon followed with over a dozen offering models today
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Aimpoint CompM2
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For the M68105 mm Rifled Tank Gun, see Royal Ordnance L7. The CompM2 is a battery-powered, non-magnifying red dot type of sight for firearms manufactured by Aimpoint AB. It was first introduced in the U. S, armed Forces in 2000, designated as the M68 Close Combat Optic. It is also known as the M68 Aimpoint and is designed to meet United States military standards, the sight is designed for use with the M16/M4 family of rifles, but can be mounted on any weapon fitted with an upper Picatinny rail. It is also NVG-compatible—the aiming dot is visible through night vision scopes and goggles. The sight is water-tight down to 25 meters and runs on one 3-volt lithium battery type 2L76 or DL1/3N, aiming dot brightness is adjustable for better visibility or increased battery life. The M68 is parallax-free at around 50 yards, meaning that the red dot will not change based on eye position at that range. At shorter ranges the point of aim will change based on eye position with the maximum error being equal to the diameter of the sights optical window at short range. The CompM2 is used across branches of the U. S, armed Forces, Sweden, and various NATO countries, among them Norway. A variant known as the ECOS-N is also issued as part of the U. S. SOPMOD kit, the sight is also available on the civilian market and is employed by various law enforcement organizations and by recreational shooters. By August 2011, the U. S. Army had bought 1,000,000 M68 Close Combat Optics, some 85 percent of Army M4s are issued with the CCO, though optics can vary depending on unit. The sight allows soldiers to engage targets out to 300 meters while keeping both eyes open for situational awareness, post combat surveys show an 85 percent acceptance rate of the CCO as an effective optic and for its value for close quarters fighting. Remaining Army rifles are issued with the M150 Rifle Combat Optic
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Holographic weapon sight
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The hologram of the reticle is built into the window and is illuminated by a laser diode. The first holographic sight was introduced by EOTech in 1998, holographic weapon sights use a laser transmission hologram of a reticle image that is recorded in three-dimensional space onto holographic film at the time of manufacture. This image is part of the viewing window. The recorded hologram is illuminated by the light of a laser diode built into the sight. The sight can be adjusted for range and windage by simply tilting or pivoting the holographic grating, like the reflector sight, the holographic sight is not parallax free, having an aim-point that can move with eye position. The optical window in a weapon sight looks like a piece of clear glass with an illuminated reticle in the middle. The aiming reticle can be a small dot whose perceived size is given by the acuity of the eye. For someone with 20/20 vision, it is about 1 minute of arc, one drawback of a holographic sight is shorter battery life when compared to reflex sights that use LEDs, such as red dot sights
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