1.
Gas
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Gas is one of the four fundamental states of matter. A pure gas may be made up of atoms, elemental molecules made from one type of atom. A gas mixture would contain a variety of pure gases much like the air, what distinguishes a gas from liquids and solids is the vast separation of the individual gas particles. This separation usually makes a colorless gas invisible to the human observer, the interaction of gas particles in the presence of electric and gravitational fields are considered negligible as indicated by the constant velocity vectors in the image. One type of commonly known gas is steam, the gaseous state of matter is found between the liquid and plasma states, the latter of which provides the upper temperature boundary for gases. Bounding the lower end of the temperature scale lie degenerative quantum gases which are gaining increasing attention, high-density atomic gases super cooled to incredibly low temperatures are classified by their statistical behavior as either a Bose gas or a Fermi gas. For a comprehensive listing of these states of matter see list of states of matter. The only chemical elements which are stable multi atom homonuclear molecules at temperature and pressure, are hydrogen, nitrogen and oxygen. These gases, when grouped together with the noble gases. Alternatively they are known as molecular gases to distinguish them from molecules that are also chemical compounds. The word gas is a neologism first used by the early 17th-century Flemish chemist J. B. van Helmont, according to Paracelsuss terminology, chaos meant something like ultra-rarefied water. An alternative story is that Van Helmonts word is corrupted from gahst and these four characteristics were repeatedly observed by scientists such as Robert Boyle, Jacques Charles, John Dalton, Joseph Gay-Lussac and Amedeo Avogadro for a variety of gases in various settings. Their detailed studies ultimately led to a relationship among these properties expressed by the ideal gas law. Gas particles are separated from one another, and consequently have weaker intermolecular bonds than liquids or solids. These intermolecular forces result from interactions between gas particles. Like-charged areas of different gas particles repel, while oppositely charged regions of different gas particles attract one another, transient, randomly induced charges exist across non-polar covalent bonds of molecules and electrostatic interactions caused by them are referred to as Van der Waals forces. The interaction of these forces varies within a substance which determines many of the physical properties unique to each gas. A comparison of boiling points for compounds formed by ionic and covalent bonds leads us to this conclusion, the drifting smoke particles in the image provides some insight into low pressure gas behavior
2.
Mass
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In physics, mass is a property of a physical body. It is the measure of a resistance to acceleration when a net force is applied. It also determines the strength of its gravitational attraction to other bodies. The basic SI unit of mass is the kilogram, Mass is not the same as weight, even though mass is often determined by measuring the objects weight using a spring scale, rather than comparing it directly with known masses. An object on the Moon would weigh less than it does on Earth because of the lower gravity and this is because weight is a force, while mass is the property that determines the strength of this force. In Newtonian physics, mass can be generalized as the amount of matter in an object, however, at very high speeds, special relativity postulates that energy is an additional source of mass. Thus, any body having mass has an equivalent amount of energy. In addition, matter is a defined term in science. There are several distinct phenomena which can be used to measure mass, active gravitational mass measures the gravitational force exerted by an object. Passive gravitational mass measures the force exerted on an object in a known gravitational field. The mass of an object determines its acceleration in the presence of an applied force, according to Newtons second law of motion, if a body of fixed mass m is subjected to a single force F, its acceleration a is given by F/m. A bodys mass also determines the degree to which it generates or is affected by a gravitational field and this is sometimes referred to as gravitational mass. The standard International System of Units unit of mass is the kilogram, the kilogram is 1000 grams, first defined in 1795 as one cubic decimeter of water at the melting point of ice. Then in 1889, the kilogram was redefined as the mass of the prototype kilogram. As of January 2013, there are proposals for redefining the kilogram yet again. In this context, the mass has units of eV/c2, the electronvolt and its multiples, such as the MeV, are commonly used in particle physics. The atomic mass unit is 1/12 of the mass of a carbon-12 atom, the atomic mass unit is convenient for expressing the masses of atoms and molecules. Outside the SI system, other units of mass include, the slug is an Imperial unit of mass, the pound is a unit of both mass and force, used mainly in the United States
3.
Atmosphere of Earth
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The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earths gravity. The atmosphere of Earth protects life on Earth by absorbing solar radiation, warming the surface through heat retention. By volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor, on average around 1% at sea level. The atmosphere has a mass of about 5. 15×1018 kg, the atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km, or 1. 57% of Earths radius, is used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km, several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earths atmosphere and its processes is called atmospheric science, early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The three major constituents of air, and therefore of Earths atmosphere, are nitrogen, oxygen, water vapor accounts for roughly 0. 25% of the atmosphere by mass. The remaining gases are often referred to as gases, among which are the greenhouse gases, principally carbon dioxide, methane, nitrous oxide. Filtered air includes trace amounts of other chemical compounds. Various industrial pollutants also may be present as gases or aerosols, such as chlorine, fluorine compounds, sulfur compounds such as hydrogen sulfide and sulfur dioxide may be derived from natural sources or from industrial air pollution. In general, air pressure and density decrease with altitude in the atmosphere, however, temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions. In this way, Earths atmosphere can be divided into five main layers, excluding the exosphere, Earth has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. It extends from the exobase, which is located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km where it merges into the solar wind. This layer is composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen. The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another, thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind, the exosphere is located too far above Earth for any meteorological phenomena to be possible
4.
Water
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Water is a transparent and nearly colorless chemical substance that is the main constituent of Earths streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that its molecule contains one oxygen, Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure, but it often refers also to its solid state or its gaseous state. It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, Water covers 71% of the Earths surface. It is vital for all forms of life. Only 2. 5% of this water is freshwater, and 98. 8% of that water is in ice and groundwater. Less than 0. 3% of all freshwater is in rivers, lakes, and the atmosphere, a greater quantity of water is found in the earths interior. Water on Earth moves continually through the cycle of evaporation and transpiration, condensation, precipitation. Evaporation and transpiration contribute to the precipitation over land, large amounts of water are also chemically combined or adsorbed in hydrated minerals. Safe drinking water is essential to humans and other even though it provides no calories or organic nutrients. There is a correlation between access to safe water and gross domestic product per capita. However, some observers have estimated that by 2025 more than half of the population will be facing water-based vulnerability. A report, issued in November 2009, suggests that by 2030, in developing regions of the world. Water plays an important role in the world economy, approximately 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers, lakes, large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a variety of chemical substances, as such it is widely used in industrial processes. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, Water is a liquid at the temperatures and pressures that are most adequate for life. Specifically, at atmospheric pressure of 1 bar, water is a liquid between the temperatures of 273.15 K and 373.15 K
5.
Viscosity
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The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the concept of thickness, for example. Viscosity is a property of the fluid which opposes the motion between the two surfaces of the fluid in a fluid that are moving at different velocities. For a given velocity pattern, the stress required is proportional to the fluids viscosity, a fluid that has no resistance to shear stress is known as an ideal or inviscid fluid. Zero viscosity is observed only at low temperatures in superfluids. Otherwise, all fluids have positive viscosity, and are said to be viscous or viscid. A fluid with a high viscosity, such as pitch. The word viscosity is derived from the Latin viscum, meaning mistletoe, the dynamic viscosity of a fluid expresses its resistance to shearing flows, where adjacent layers move parallel to each other with different speeds. It can be defined through the situation known as a Couette flow. This fluid has to be homogeneous in the layer and at different shear stresses, if the speed of the top plate is small enough, the fluid particles will move parallel to it, and their speed will vary linearly from zero at the bottom to u at the top. Each layer of fluid will move faster than the one just below it, in particular, the fluid will apply on the top plate a force in the direction opposite to its motion, and an equal but opposite one to the bottom plate. An external force is required in order to keep the top plate moving at constant speed. The magnitude F of this force is found to be proportional to the u and the area A of each plate. The proportionality factor μ in this formula is the viscosity of the fluid, the ratio u/y is called the rate of shear deformation or shear velocity, and is the derivative of the fluid speed in the direction perpendicular to the plates. Isaac Newton expressed the forces by the differential equation τ = μ ∂ u ∂ y, where τ = F/A. This formula assumes that the flow is moving along parallel lines and this equation can be used where the velocity does not vary linearly with y, such as in fluid flowing through a pipe. Use of the Greek letter mu for the dynamic viscosity is common among mechanical and chemical engineers. However, the Greek letter eta is used by chemists, physicists
6.
Geophone
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A geophone is a device that converts ground movement into voltage, which may be recorded at a recording station. The deviation of this voltage from the base line is called the seismic response and is analyzed for structure of the earth. The term geophone derives from the Greek word γῆ meaning earth, geophones have historically been passive analog devices and typically comprise a spring-mounted magnetic mass moving within a wire coil to generate an electrical signal. The response of a geophone is proportional to ground velocity. MEMS have a higher noise level than geophones and can only be used in strong motion or active seismic applications. The frequency response of a geophone is that of an oscillator, fully determined by corner frequency. Since the corner frequency is proportional to the root of the moving mass. It is possible to lower the corner electronically, at the price of higher noise. Although waves passing through the earth have a nature, geophones are normally constrained to respond to single dimension - usually the vertical. However, some require the full wave to be used. In analog devices, three moving coil elements are mounted in an arrangement within a single case. The majority of geophones are used in seismology to record the energy waves reflected by the subsurface geology. In this case the primary interest is in the motion of the Earths surface. However, not all the waves are upwards travelling, a strong, horizontally transmitted wave known as ground-roll also generates vertical motion that can obliterate the weaker vertical signals. By using large areal arrays tuned to the wavelength of the ground-roll the dominant noise signals can be attenuated, analog geophones are very sensitive devices which can respond to very distant tremors. These small signals can be drowned by larger signals from local sources and it is possible though to recover the small signals caused by large but distant events by correlating signals from several geophones deployed in an array. Signals which are registered only at one or few geophones can be attributed to unwanted, local events and it can be assumed that small signals that register uniformly at all geophones in an array can be attributed to a distant and therefore significant event. The sensitivity of passive geophones is typically 30 Volts/, so they are in general not a replacement for broadband seismometers, conversely, some applications of geophones are interested only in very local events
7.
Microphone
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A microphone, colloquially nicknamed mic or mike, is a transducer that converts sound into an electrical signal. Several different types of microphone are in use, which employ different methods to convert the air pressure variations of a wave to an electrical signal. Microphones typically need to be connected to a preamplifier before the signal can be recorded or reproduced, in order to speak to larger groups of people, a need arose to increase the volume of the human voice. The earliest devices used to achieve this were acoustic megaphones, some of the first examples, from fifth century BC Greece, were theater masks with horn-shaped mouth openings that acoustically amplified the voice of actors in amphitheatres. In 1665, the English physicist Robert Hooke was the first to experiment with an other than air with the invention of the lovers telephone made of stretched wire with a cup attached at each end. German inventor Johann Philipp Reis designed an early sound transmitter that used a strip attached to a vibrating membrane that would produce intermittent current. Better results were achieved with the transmitter design in Scottish-American Alexander Graham Bells telephone of 1876 – the diaphragm was attached to a conductive rod in an acid solution. These systems, however, gave a poor sound quality. The first microphone that enabled proper voice telephony was the carbon microphone and this was independently developed by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, the carbon microphone is the direct prototype of todays microphones and was critical in the development of telephony, broadcasting and the recording industries. Thomas Edison refined the carbon microphone into his carbon-button transmitter of 1886 and this microphone was employed at the first ever radio broadcast, a performance at the New York Metropolitan Opera House in 1910. In 1916, E. C. Wente of Western Electric developed the next breakthrough with the first condenser microphone, in 1923, the first practical moving coil microphone was built. The Marconi Skykes or magnetophon, developed by Captain H. J. Round, was the standard for BBC studios in London and this was improved in 1930 by Alan Blumlein and Herbert Holman who released the HB1A and was the best standard of the day. Also in 1923, the microphone was introduced, another electromagnetic type, believed to have been developed by Harry F. Olson. Over the years these microphones were developed by companies, most notably RCA that made large advancements in pattern control. With television and film technology booming there was demand for high fidelity microphones, electro-Voice responded with their Academy Award-winning shotgun microphone in 1963. During the second half of 20th century development advanced quickly with the Shure Brothers bringing out the SM58, digital was pioneered by Milab in 1999 with the DM-1001. The latest research developments include the use of optics, lasers and interferometers
8.
Seismometer
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Seismometers are instruments that measure motion of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions, and other seismic sources. Records of seismic waves allow seismologists to map the interior of the Earth, the seismometer was invented by the Chinese polymath Zhang Heng in AD132 during the Han dynasty. The first Western description of a comes from the French physicist and priest Jean de Hautefeuille in 1703. The modern seismometer was developed in the 19th century by John Milne, James Alfred Ewing, seismograph is another Greek term from seismós and γράφω, gráphō, to draw. The concerning technical discipline is called seismometry, a branch of seismology, a simple seismometer that is sensitive to up-down motions of the earth can be understood by visualizing a weight hanging on a spring. The spring and weight are suspended from a frame that moves along with the earthʼs surface, as the earth moves, the relative motion between the weight and the earth provides a measure of the vertical ground motion. Any movement of the moves the frame. The mass tends not to move because of its inertia, early seismometers used optical levers or mechanical linkages to amplify the small motions involved, recording on soot-covered paper or photographic paper. In some systems, the mass is held nearly motionless relative to the frame by a negative feedback loop. The motion of the relative to the frame is measured. The voltage needed to produce this force is the output of the seismometer, in other systems the weight is allowed to move, and its motion produces a voltage in a coil attached to the mass and moving through the magnetic field of a magnet attached to the frame. This design is used in the geophones used in seismic surveys for oil. Professional seismic observatories usually have instruments measuring three axes, north-south, east-west, and the vertical, if only one axis is measured, this is usually the vertical because it is less noisy and gives better records of some seismic waves. The foundation of a station is critical. A professional station is mounted on bedrock. The best mountings may be in deep boreholes, which avoid thermal effects, ground noise and tilting from weather, other instruments are often mounted in insulated enclosures on small buried piers of unreinforced concrete. Reinforcing rods and aggregates would distort the pier as the temperature changes, a site is always surveyed for ground noise with a temporary installation before pouring the pier and laying conduit. Originally, European seismographs were placed in an area after a destructive earthquake
9.
Defect detector
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A defect detector is a device used on railroads to detect axle and signal problems in passing trains. The detectors are normally integrated into the tracks and often include sensors to detect different kinds of problems that could occur. The use of defect detectors has since spread to other overseas railroads, to detect hotboxes, i. e. overheating bearings, they would look for oil smoke during the day or a red glow at night. As early as the 1940s, automatic defect detectors were installed to improve upon the manual process, the detectors would transmit their data via wired links to remote read-outs in stations, offices or interlocking towers. A stylus-and-cylinder gauge would record a reading for every axle, if a journal were too hot, or if some other defect were detected, early line-side defect detectors were typically housed in concrete bungalows, roughly every 10–20 miles. The crew stationed at the rear of the train would observe this light and, if a defect were indicated, the first computerized detectors used fixed-display boards. These had a numeric display and a number of indicator lights relating to the nature of defects. A number would be displayed in lights on the board after the train had cleared the detector, the number 000 meant there were no defects, any other number warned of a defect at the corresponding axle. If several were detected, small white lights on the top and bottom could also be displayed to inform the crews of multiple problems. Nevertheless, the conductor was still required to go into the bungalow, seaboard Air Line was the first railroad to install talking defect detectors. Beginning in the 1960s, their crews could hear the results of hotbox and dragging-equipment checks spoken over their radios in the engine cab. Over the years, as the use of this technology accelerated, for example, computerized, talking detectors allowed crews to interact with the detector using a touch tone function on their radios to recall the latest defect report. This eliminated any need for crews to walk to the location to confirm the radio reading. Sometimes the locations ambient temperature and train speed are also noted by the mechanical voice, crews can use their touch-tone hand radios to get the detector to repeat error messages. Defect detectors that are equipped with such a voice are often called talking detectors by railfans. To this day some rail lines, mostly passenger routes with a high traffic density, maintain centralized readout. This is due to the large and confusing volume of traffic a talking detector would generate. When an error signal is received a dispatcher or operator will contact the train via radio manually transmitting the error message, today defect detectors are often incorporated in monitoring platforms that are primarily used by railroads to more closely monitor the status of their trains
10.
Radar gun
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A radar speed gun is a device used to measure the speed of moving objects. A radar speed gun is a Doppler radar unit that may be hand-held, vehicle-mounted or static. The radar speed gun was invented by John L. Barker Sr. and Ben Midlock, originally, Automatic Signal was approached by Grumman Aircraft Corporation to solve the specific problem of terrestrial landing gear damage on the now-legendary PBY Catalina amphibious aircraft. Barker and Midlock cobbled a Doppler radar unit from coffee cans soldered shut to make microwave resonators, the unit was installed at the end of the runway, and aimed directly upward to measure the sink rate of landing PBYs. After the war, Barker and Midlock tested radar on the Merritt Parkway, in 1947, the system was tested by the Connecticut State Police in Glastonbury, Connecticut, initially for traffic surveys and issuing warnings to drivers for excessive speed. Starting in February 1949, the police began to issue speeding tickets based on the speed recorded by the radar device. In 1948, radar was used in Garden City, New York. Speed guns use Doppler radar to perform speed measurements, Radar speed guns, like other types of radar, consist of a radio transmitter and receiver. They send out a signal in a narrow beam, then receive the same signal back after it bounces off the target object. From that difference, the radar speed gun can calculate the speed of the object from which the waves have been bounced. After the returning waves are received, a signal with a equal to this difference is created by mixing the received radio signal with a little of the transmitted signal. Since this type of speed gun measures the difference in speed between a target and the gun itself, the gun must be stationary in order to give a correct reading. Instead of comparing the frequency of the signal reflected from the target with the transmitted signal, the frequency difference between these two signals gives the true speed of the target vehicle. Modern radar speed guns normally operate at X, K, Ka, Radar guns that operate using the X band frequency range are becoming less common because they produce a strong and easily detectable beam. Also, most automatic doors utilize radio waves in the X band range, as a result, K band and Ka band are most commonly used by police agencies. For these reasons, hand-held radar typically includes an on-off trigger, Radar detectors are illegal in some areas. Traffic radar comes in many models, hand-held units are mostly battery powered, and for the most part are used as stationary speed enforcement tools. Stationary radar can be mounted in vehicles and may have one or two antennae
11.
Speedometer
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A speedometer or a speed meter is a gauge that measures and displays the instantaneous speed of a vehicle. Now universally fitted to vehicles, they started to be available as options in the 1900s. Speedometers for other vehicles have specific names and use other means of sensing speed, for a boat, this is a pit log. For an aircraft, this is an airspeed indicator, charles Babbage is credited with creating an early type of a speedometer, which were usually fitted to locomotives. The electric speedometer was invented by the Croatian Josip Belušić in 1888, originally patented by Otto Schultze on October 7,1902, it uses a rotating flexible cable usually driven by gearing linked to the output of the vehicles transmission. The early Volkswagen Beetle and many motorcycles, however, use a cable driven from a front wheel, when the car or motorcycle is in motion, a speedometer gear assembly turns a speedometer cable, which then turns the speedometer mechanism itself. A small permanent magnet affixed to the speedometer cable interacts with an aluminum cup attached to the shaft of the pointer on the analogue speedometer instrument. As the magnet rotates near the cup, the magnetic field produces eddy currents in the cup. The effect is that the magnet exerts a torque on the cup, dragging it, the pointer shaft is held toward zero by a fine torsion spring. The torque on the cup increases with the speed of rotation of the magnet, thus an increase in the speed of the car will twist the cup and speedometer pointer against the spring. The cup and pointer will turn until the torque of the currents on the cup is balanced by the opposing torque of the spring. At a given speed the pointer will remain motionless and pointing to the number on the speedometers dial. The return spring is calibrated such that a given speed of the cable corresponds to a specific speed indication on the speedometer. The sensor is typically a set of one or more magnets mounted on the shaft or differential crownwheel. As the part in question turns, the magnets or teeth pass beneath the sensor, alternatively, in more recent designs, some manufactures rely on pulses coming from the ABS wheel sensors. Most modern electronic speedometers have the additional ability over the current type to show the vehicle speed when moving in reverse gear. A computer converts the pulses to a speed and displays this speed on an electronically controlled, another early form of electronic speedometer relies upon the interaction between a precision watch mechanism and a mechanical pulsator driven by the cars wheel or transmission. The watch mechanism endeavors to push the speedometer pointer toward zero, the position of the speedometer pointer reflects the relative magnitudes of the outputs of the two mechanisms
12.
Frequency
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Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as frequency, which emphasizes the contrast to spatial frequency. The period is the duration of time of one cycle in a repeating event, for example, if a newborn babys heart beats at a frequency of 120 times a minute, its period—the time interval between beats—is half a second. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as vibrations, audio signals, radio waves. For cyclical processes, such as rotation, oscillations, or waves, in physics and engineering disciplines, such as optics, acoustics, and radio, frequency is usually denoted by a Latin letter f or by the Greek letter ν or ν. For a simple motion, the relation between the frequency and the period T is given by f =1 T. The SI unit of frequency is the hertz, named after the German physicist Heinrich Hertz, a previous name for this unit was cycles per second. The SI unit for period is the second, a traditional unit of measure used with rotating mechanical devices is revolutions per minute, abbreviated r/min or rpm. As a matter of convenience, longer and slower waves, such as ocean surface waves, short and fast waves, like audio and radio, are usually described by their frequency instead of period. Spatial frequency is analogous to temporal frequency, but the axis is replaced by one or more spatial displacement axes. Y = sin = sin d θ d x = k Wavenumber, in the case of more than one spatial dimension, wavenumber is a vector quantity. For periodic waves in nondispersive media, frequency has a relationship to the wavelength. Even in dispersive media, the frequency f of a wave is equal to the phase velocity v of the wave divided by the wavelength λ of the wave. In the special case of electromagnetic waves moving through a vacuum, then v = c, where c is the speed of light in a vacuum, and this expression becomes, f = c λ. When waves from a monochrome source travel from one medium to another, their remains the same—only their wavelength. For example, if 71 events occur within 15 seconds the frequency is, the latter method introduces a random error into the count of between zero and one count, so on average half a count. This is called gating error and causes an error in the calculated frequency of Δf = 1/, or a fractional error of Δf / f = 1/ where Tm is the timing interval. This error decreases with frequency, so it is a problem at low frequencies where the number of counts N is small, an older method of measuring the frequency of rotating or vibrating objects is to use a stroboscope
