1.
Prism
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In optics, a prism is a transparent optical element with flat, polished surfaces that refract light. At least two of the surfaces must have an angle between them. The exact angles between the surfaces depend on the application, the traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use prism usually refers to this type. Some types of optical prism are not in fact in the shape of geometric prisms, prisms can be made from any material that is transparent to the wavelengths for which they are designed. Typical materials include glass, plastic and fluorite, a dispersive prism can be used to break light up into its constituent spectral colors. Furthermore, prisms can be used to light, or to split light into components with different polarizations. Light changes speed as it moves from one medium to another and this speed change causes the light to be refracted and to enter the new medium at a different angle. The degree of bending of the lights path depends on the angle that the incident beam of light makes with the surface, the refractive index of many materials varies with the wavelength or color of the light used, a phenomenon known as dispersion. This causes light of different colors to be refracted differently and to leave the prism at different angles and this can be used to separate a beam of white light into its constituent spectrum of colors. Prisms will generally disperse light over a larger frequency bandwidth than diffraction gratings. Furthermore, prisms do not suffer from complications arising from overlapping spectral orders, prisms are sometimes used for the internal reflection at the surfaces rather than for dispersion. If light inside the prism hits one of the surfaces at a steep angle, total internal reflection occurs. This makes a prism a useful substitute for a mirror in some situations, ray angle deviation and dispersion through a prism can be determined by tracing a sample ray through the element and using Snells law at each interface. For the prism shown at right, the angles are given by θ0 ′ = arcsin θ1 = α − θ0 ′ θ1 ′ = arcsin θ2 = θ1 ′ − α. All angles are positive in the shown in the image. For a prism in air n 0 = n 2 ≃1 and this allows the nonlinear equation in the deviation angle δ to be approximated by δ ≈ θ0 − α + = θ0 − α + n α − θ0 = α. The deviation angle depends on wavelength through n, so for a thin prism the deviation angle varies with wavelength according to δ ≈ α, before Isaac Newton, it was believed that white light was colorless, and that the prism itself produced the color. It was only later that Young and Fresnel combined Newtons particle theory with Huygens wave theory to show that color is the manifestation of lights wavelength
2.
Optics
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Optics is the branch of physics which involves the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviolet, and infrared light, because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties. Most optical phenomena can be accounted for using the classical description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice, practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines, physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometric optics. Historically, the model of light was developed first, followed by the wave model of light. Progress in electromagnetic theory in the 19th century led to the discovery that waves were in fact electromagnetic radiation. Some phenomena depend on the fact that light has both wave-like and particle-like properties, explanation of these effects requires quantum mechanics. When considering lights particle-like properties, the light is modelled as a collection of particles called photons, quantum optics deals with the application of quantum mechanics to optical systems. Optical science is relevant to and studied in many related disciplines including astronomy, various engineering fields, photography, practical applications of optics are found in a variety of technologies and everyday objects, including mirrors, lenses, telescopes, microscopes, lasers, and fibre optics. Optics began with the development of lenses by the ancient Egyptians and Mesopotamians, the earliest known lenses, made from polished crystal, often quartz, date from as early as 700 BC for Assyrian lenses such as the Layard/Nimrud lens. The ancient Romans and Greeks filled glass spheres with water to make lenses, the word optics comes from the ancient Greek word ὀπτική, meaning appearance, look. Greek philosophy on optics broke down into two opposing theories on how vision worked, the theory and the emission theory. The intro-mission approach saw vision as coming from objects casting off copies of themselves that were captured by the eye, plato first articulated the emission theory, the idea that visual perception is accomplished by rays emitted by the eyes. He also commented on the parity reversal of mirrors in Timaeus, some hundred years later, Euclid wrote a treatise entitled Optics where he linked vision to geometry, creating geometrical optics. Ptolemy, in his treatise Optics, held a theory of vision, the rays from the eye formed a cone, the vertex being within the eye. The rays were sensitive, and conveyed back to the observer’s intellect about the distance. He summarised much of Euclid and went on to describe a way to measure the angle of refraction, during the Middle Ages, Greek ideas about optics were resurrected and extended by writers in the Muslim world
3.
Triangular prism
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In geometry, a triangular prism is a three-sided prism, it is a polyhedron made of a triangular base, a translated copy, and 3 faces joining corresponding sides. A right triangular prism has rectangular sides, otherwise it is oblique, a uniform triangular prism is a right triangular prism with equilateral bases, and square sides. Equivalently, it is a polyhedron of which two faces are parallel, while the normals of the other three are in the same plane. All cross-sections parallel to the faces are the same triangle. A right triangular prism is semiregular or, more generally, a uniform if the base faces are equilateral triangles. It can be seen as a truncated trigonal hosohedron, represented by Schläfli symbol t, alternately it can be seen as the Cartesian product of a triangle and a line segment, and represented by the product x. The dual of a prism is a triangular bipyramid. The symmetry group of a right 3-sided prism with triangular base is D3h of order 12, the rotation group is D3 of order 6. The symmetry group does not contain inversion, the volume of any prism is the product of the area of the base and the distance between the two bases. A truncated right triangular prism has one triangular face truncated at an oblique angle, there are two full D2h symmetry facetings of a triangular prism, both with 6 isosceles triangle faces, one keeping the original top and bottom triangles, and one the original squares. Two lower C3v symmetry faceting have one triangle,3 lateral crossed square faces. This polyhedron is topologically related as a part of sequence of uniform truncated polyhedra with vertex configurations and this polyhedron is topologically related as a part of sequence of cantellated polyhedra with vertex figure, and continues as tilings of the hyperbolic plane. These vertex-transitive figures have reflectional symmetry and this polyhedron is topologically related as a part of sequence of cantellated polyhedra with vertex figure, and continues as tilings of the hyperbolic plane. These vertex-transitive figures have reflectional symmetry, there are 4 uniform compounds of triangular prisms, Compound of four triangular prisms, compound of eight triangular prisms, compound of ten triangular prisms, compound of twenty triangular prisms. Each progressive uniform polytope is constructed vertex figure of the previous polytope, thorold Gosset identified this series in 1900 as containing all regular polytope facets, containing all simplexes and orthoplexes. In Coxeters notation the triangular prism is given the symbol −121, the triangular prism exists as cells of a number of four-dimensional uniform 4-polytopes, including, Wedge Weisstein, Eric W. Triangular prism. Interactive Polyhedron, Triangular Prism surface area and volume of a triangular prism
4.
Spectroscopy
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Spectroscopy /spɛkˈtrɒskəpi/ is the study of the interaction between matter and electromagnetic radiation. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, later the concept was expanded greatly to include any interaction with radiative energy as a function of its wavelength or frequency. Spectroscopic data is represented by an emission spectrum, a plot of the response of interest as a function of wavelength or frequency. Spectroscopy and spectrography are terms used to refer to the measurement of radiation intensity as a function of wavelength and are used to describe experimental spectroscopic methods. Spectral measurement devices are referred to as spectrometers, spectrophotometers, spectrographs or spectral analyzers, daily observations of color can be related to spectroscopy. Neon lighting is an application of atomic spectroscopy. Neon and other noble gases have characteristic emission frequencies, neon lamps use collision of electrons with the gas to excite these emissions. Inks, dyes and paints include chemical compounds selected for their characteristics in order to generate specific colors. A commonly encountered molecular spectrum is that of nitrogen dioxide, gaseous nitrogen dioxide has a characteristic red absorption feature, and this gives air polluted with nitrogen dioxide a reddish-brown color. Rayleigh scattering is a spectroscopic scattering phenomenon that accounts for the color of the sky, Spectroscopy is used in physical and analytical chemistry because atoms and molecules have unique spectra. As a result, these spectra can be used to detect, identify and quantify information about the atoms, Spectroscopy is also used in astronomy and remote sensing on earth. The measured spectra are used to determine the composition and physical properties of astronomical objects. One of the concepts in spectroscopy is a resonance and its corresponding resonant frequency. Resonances were first characterized in mechanical systems such as pendulums, mechanical systems that vibrate or oscillate will experience large amplitude oscillations when they are driven at their resonant frequency. A plot of amplitude vs. excitation frequency will have a peak centered at the resonance frequency and this plot is one type of spectrum, with the peak often referred to as a spectral line, and most spectral lines have a similar appearance. In quantum mechanical systems, the resonance is a coupling of two quantum mechanical stationary states of one system, such as an atom, via an oscillatory source of energy such as a photon. The coupling of the two states is strongest when the energy of the matches the energy difference between the two states. The energy of a photon is related to its frequency by E = h ν where h is Plancks constant, spectra of atoms and molecules often consist of a series of spectral lines, each one representing a resonance between two different quantum states
5.
Dispersion (optics)
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In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency. Media having this property may be termed dispersive media. Sometimes the term chromatic dispersion is used for specificity, the most familiar example of dispersion is probably a rainbow, in which dispersion causes the spatial separation of a white light into components of different wavelengths. Most often, chromatic dispersion refers to material dispersion, that is. However, in a waveguide there is also the phenomenon of waveguide dispersion, more generally, waveguide dispersion can occur for waves propagating through any inhomogeneous structure, whether or not the waves are confined to some region. In a waveguide, both types of dispersion will generally be present, although they are not strictly additive, for example, in fiber optics the material and waveguide dispersion can effectively cancel each other out to produce a zero-dispersion wavelength, important for fast fiber-optic communication. Material dispersion can be a desirable or undesirable effect in optical applications, the dispersion of light by glass prisms is used to construct spectrometers and spectroradiometers. Holographic gratings are used, as they allow more accurate discrimination of wavelengths. However, in lenses, dispersion causes chromatic aberration, an effect that may degrade images in microscopes, telescopes. The phase velocity, v, of a wave in a uniform medium is given by v = c n where c is the speed of light in a vacuum. In general, the index is some function of the frequency f of the light, thus n = n, or alternatively. The wavelength dependence of a refractive index is usually quantified by its Abbe number or its coefficients in an empirical formula such as the Cauchy or Sellmeier equations. In particular, for materials, the susceptibility χ that appears in the Kramers–Kronig relations is the electric susceptibility χe = n2 −1. The most commonly seen consequence of dispersion in optics is the separation of light into a color spectrum by a prism. From Snells law it can be seen that the angle of refraction of light in a prism depends on the index of the prism material. For visible light, refraction indices n of most transparent materials decrease with increasing wavelength λ,1 < n < n < n, or alternatively, in this case, the medium is said to have normal dispersion. Whereas, if the index increases with increasing wavelength, the medium is said to have anomalous dispersion, at the interface of such a material with air or vacuum, Snells law predicts that light incident at an angle θ to the normal will be refracted at an angle arcsin. Thus, blue light, with a refractive index, will be bent more strongly than red light
6.
Spectrum
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A spectrum is a condition that is not limited to a specific set of values but can vary, without steps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors in visible light after passing through a prism, as scientific understanding of light advanced, it came to apply to the entire electromagnetic spectrum. Spectrum has since been applied by analogy to topics outside of optics, thus, one might talk about the spectrum of political opinion, or the spectrum of activity of a drug, or the autism spectrum. In these uses, values within a spectrum may not be associated with precisely quantifiable numbers or definitions, such uses imply a broad range of conditions or behaviors grouped together and studied under a single title for ease of discussion. Nonscientific uses of the spectrum are sometimes misleading. For instance, a single left–right spectrum of opinion does not capture the full range of peoples political beliefs. Political scientists use a variety of biaxial and multiaxial systems to accurately characterize political opinion. In most modern usages of spectrum there is a theme between the extremes at either end. This was not always true in older usage, in Latin spectrum means image or apparition, including the meaning spectre. Spectral evidence is testimony about what was done by spectres of persons not present physically and it was used to convict a number of persons of witchcraft at Salem, Massachusetts in the late 17th century. The word spectrum was used to designate a ghostly optical afterimage by Goethe in his Theory of Colors and Schopenhauer in On Vision. The prefix spectro- is used to form words relating to spectra, for example, a spectrometer is a device used to record spectra and spectroscopy is the use of a spectrometer for chemical analysis. In the 17th century the word spectrum was introduced into optics by Isaac Newton, soon the term referred to a plot of light intensity or power as a function of frequency or wavelength, also known as a spectral density plot. The term spectrum was expanded to apply to other waves, such as sound waves that could also be measured as a function of frequency, frequency spectrum and power spectrum of a signal. The term now applies to any signal that can be measured or decomposed along a variable such as energy in electron spectroscopy or mass to charge ratio in mass spectrometry. Spectrum is also used to refer to a representation of the signal as a function of the dependent variable. Devices used to measure an electromagnetic spectrum are called spectrograph or spectrometer, the visible spectrum is the part of the electromagnetic spectrum that can be seen by the human eye. The wavelength of light ranges from 390 to 700 nm
7.
Color
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Color or colour is the characteristic of human visual perception described through color categories, with names such as red, yellow, purple, or blue. This perception of color derives from the stimulation of cells in the human eye by electromagnetic radiation in the spectrum of light. Color categories and physical specifications of color are associated with objects through the wavelength of the light that is reflected from them and this reflection is governed by the objects physical properties such as light absorption, emission spectra, etc. By defining a color space, colors can be identified numerically by coordinates, there may also be more than three color dimensions in other color spaces, such as in the CMYK color model, wherein one of the dimensions relates to a colours colorfulness). The photo-receptivity of the eyes of species also varies considerably from our own. Honeybees and bumblebees for instance have trichromatic color vision sensitive to ultraviolet but is insensitive to red, papilio butterflies possess six types of photoreceptors and may have pentachromatic vision. The most complex color vision system in the kingdom has been found in stomatopods with up to 12 spectral receptor types thought to work as multiple dichromatic units. The science of color is sometimes called chromatics, colorimetry, or simply color science and it includes the perception of color by the human eye and brain, the origin of color in materials, color theory in art, and the physics of electromagnetic radiation in the visible range. Electromagnetic radiation is characterized by its wavelength and its intensity, when the wavelength is within the visible spectrum, it is known as visible light. Most light sources emit light at different wavelengths, a sources spectrum is a distribution giving its intensity at each wavelength. Although the spectrum of light arriving at the eye from a given direction determines the color sensation in that direction, in each such class the members are called metamers of the color in question. The table at right shows approximate frequencies and wavelengths for various pure spectral colors, the wavelengths listed are as measured in air or vacuum. A common list identifies six main bands, red, orange, yellow, green, blue, Newtons conception included a seventh color, indigo, between blue and violet. It is possible that what Newton referred to as blue is nearer to what today is known as cyan, the color of an object depends on both the physics of the object in its environment and the characteristics of the perceiving eye and brain. Some objects not only light, but also transmit light or emit light themselves. This effect is known as color constancy, opaque objects that do not reflect specularly have their color determined by which wavelengths of light they scatter strongly. If objects scatter all wavelengths with roughly equal strength, they appear white, if they absorb all wavelengths, they appear black. Opaque objects that reflect light of different wavelengths with different efficiencies look like mirrors tinted with colors determined by those differences
8.
Rainbow
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A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured arc, Rainbows caused by sunlight always appear in the section of sky directly opposite the sun. However, the observer sees only an arc formed by illuminated droplets above the ground. In a primary rainbow, the arc shows red on the outer part and this rainbow is caused by light being refracted when entering a droplet of water, then reflected inside on the back of the droplet and refracted again when leaving it. In a double rainbow, an arc is seen outside the primary arc. A rainbow is not located at a distance from the observer. Thus, a rainbow is not an object and cannot be physically approached, indeed, it is impossible for an observer to see a rainbow from water droplets at any angle other than the customary one of 42 degrees from the direction opposite the light source. Even if an observer sees another observer who seems under or at the end of a rainbow, Rainbows span a continuous spectrum of colours. Rainbows can be caused by many forms of airborne water and these include not only rain, but also mist, spray, and airborne dew. Rainbows can be observed there are water drops in the air. Because of this, rainbows are seen in the western sky during the morning. The most spectacular rainbow displays happen when half the sky is dark with raining clouds. The result is a rainbow that contrasts with the darkened background. During such good visibility conditions, the larger but fainter secondary rainbow is often visible and it appears about 10° outside of the primary rainbow, with inverse order of colours. The rainbow effect is commonly seen near waterfalls or fountains. In addition, the effect can be created by dispersing water droplets into the air during a sunny day. Rarely, a moonbow, lunar rainbow or nighttime rainbow, can be seen on strongly moonlit nights, as human visual perception for colour is poor in low light, moonbows are often perceived to be white. It is difficult to photograph the complete semicircle of a rainbow in one frame, for a 35 mm camera, a wide-angle lens with a focal length of 19 mm or less would be required
9.
Index of refraction
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In optics, the refractive index or index of refraction n of a material is a dimensionless number that describes how light propagates through that medium. It is defined as n = c v, where c is the speed of light in vacuum, for example, the refractive index of water is 1.333, meaning that light travels 1.333 times faster in a vacuum than it does in water. The refractive index determines how light is bent, or refracted. The refractive indices also determine the amount of light that is reflected when reaching the interface, as well as the angle for total internal reflection. This implies that vacuum has a index of 1. The refractive index varies with the wavelength of light and this is called dispersion and causes the splitting of white light into its constituent colors in prisms and rainbows, and chromatic aberration in lenses. Light propagation in absorbing materials can be described using a refractive index. The imaginary part then handles the attenuation, while the real part accounts for refraction, the concept of refractive index is widely used within the full electromagnetic spectrum, from X-rays to radio waves. It can also be used with wave phenomena such as sound, in this case the speed of sound is used instead of that of light and a reference medium other than vacuum must be chosen. Thomas Young was presumably the person who first used, and invented, at the same time he changed this value of refractive power into a single number, instead of the traditional ratio of two numbers. The ratio had the disadvantage of different appearances, newton, who called it the proportion of the sines of incidence and refraction, wrote it as a ratio of two numbers, like 529 to 396. Hauksbee, who called it the ratio of refraction, wrote it as a ratio with a fixed numerator, hutton wrote it as a ratio with a fixed denominator, like 1.3358 to 1. Young did not use a symbol for the index of refraction, in the next years, others started using different symbols, n, m, and µ. For visible light most transparent media have refractive indices between 1 and 2, a few examples are given in the adjacent table. These values are measured at the yellow doublet D-line of sodium, with a wavelength of 589 nanometers, gases at atmospheric pressure have refractive indices close to 1 because of their low density. Almost all solids and liquids have refractive indices above 1.3, aerogel is a very low density solid that can be produced with refractive index in the range from 1.002 to 1.265. Moissanite lies at the end of the range with a refractive index as high as 2.65. Most plastics have refractive indices in the range from 1.3 to 1.7, for infrared light refractive indices can be considerably higher
10.
Snell's law
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In optics, the law is used in ray tracing to compute the angles of incidence or refraction, and in experimental optics to find the refractive index of a material. The law is also satisfied in metamaterials, which light to be bent backward at a negative angle of refraction with a negative refractive index. Although named after Dutch astronomer Willebrord Snellius, the law was first accurately described by the scientist Ibn Sahl at the Baghdad court in 984, in the manuscript On Burning Mirrors and Lenses, Sahl used the law to derive lens shapes that focus light with no geometric aberrations. The law follows from Fermats principle of least time, which in turn follows from the propagation of light as waves, ptolemy, a Greek living in Alexandria, Egypt, had found a relationship regarding refraction angles, but it was inaccurate for angles that were not small. Ptolemy was confident he had found an empirical law, partially as a result of fudging his data to fit theory. Alhazen, in his Book of Optics, came closer to discovering the law of refraction, although named after Dutch astronomer Willebrord Snellius, the law was first accurately described by the Persian scientist Ibn Sahl at the Baghdad court in 984. In the manuscript On Burning Mirrors and Lenses, Sahl used the law to derive lens shapes that focus light with no geometric aberrations. The law was rediscovered by Thomas Harriot in 1602, who however did not publish his results although he had corresponded with Kepler on this very subject, in 1621, Willebrord Snellius derived a mathematically equivalent form, that remained unpublished during his lifetime. René Descartes independently derived the law using heuristic momentum conservation arguments in terms of sines in his 1637 essay Dioptrics, rejecting Descartes solution, Pierre de Fermat arrived at the same solution based solely on his principle of least time. Interestingly, Descartes assumed the speed of light was infinite, yet in his derivation of Snells law he also assumed the denser the medium, the greater the speed of light. Fermat supported the assumptions, i. e. the speed of light is finite. Fermats derivation also utilized his invention of adequality, a mathematical equivalent to differential calculus, for finding maxima, minima. In his influential mathematics book Geometry, Descartes solves a problem that was worked on by Apollonius of Perga, given n lines L and a point P on each line, find the locus of points Q such that the lengths of the line segments QP satisfy certain conditions. For example, when n =4, given the lines a, b, c, and d and a point A on a, B on b, and so on, find the locus of points Q such that the product QA*QB equals the product QC*QD. When the lines are not all parallel, Pappus showed that the loci are conics, to show that the cubic curves were interesting, he showed that they arose naturally in optics from Snells law. According to Dijksterhuis, In De natura lucis et proprietate Isaac Vossius said that Descartes had seen Snells paper and we now know this charge to be undeserved but it has been adopted many times since. Both Fermat and Huygens repeated this accusation that Descartes had copied Snell, in French, Snells Law is called la loi de Descartes or loi de Snell-Descartes. As the development of optical and electromagnetic theory, the ancient Snells law was brought into a new stage
11.
Max Born
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Max Born was a German physicist and mathematician who was instrumental in the development of quantum mechanics. He also made contributions to physics and optics and supervised the work of a number of notable physicists in the 1920s and 1930s. Born won the 1954 Nobel Prize in Physics for his research in Quantum Mechanics. He wrote his Ph. D. thesis on the subject of Stability of Elastica in a Plane and Space, in 1905, he began researching special relativity with Minkowski, and subsequently wrote his habilitation thesis on the Thomson model of the atom. In the First World War, after originally being placed as a radio operator, in 1921, Born returned to Göttingen, arranging another chair for his long-time friend and colleague James Franck. Under Born, Göttingen became one of the worlds foremost centres for physics, in 1925, Born and Werner Heisenberg formulated the matrix mechanics representation of quantum mechanics. The following year, he formulated the now-standard interpretation of the probability density function for ψ*ψ in the Schrödinger equation and his influence extended far beyond his own research. Max Delbrück, Siegfried Flügge, Friedrich Hund, Pascual Jordan, Maria Goeppert-Mayer, Lothar Wolfgang Nordheim, Robert Oppenheimer, in January 1933, the Nazi Party came to power in Germany, and Born, who was Jewish, was suspended. Max Born became a naturalised British subject on 31 August 1939 and he remained at Edinburgh until 1952. He retired to Bad Pyrmont, in West Germany, and died in a hospital in Göttingen on 5 January 1970. Max Born was born on 11 December 1882 in Breslau, which at the time of Borns birth was part of the Prussian Province of Silesia in the German Empire and she died when Max was four years old, on 29 August 1886. Max had a sister, Käthe, who was born in 1884, Wolfgang later became Professor of Art History at the City College of New York. Initially educated at the König-Wilhelm-Gymnasium in Breslau, Born entered the University of Breslau in 1901, the German university system allowed students to move easily from one university to another, so he spent summer semesters at Heidelberg University in 1902 and the University of Zurich in 1903. Fellow students at Breslau, Otto Toeplitz and Ernst Hellinger, told Born about the University of Göttingen, at Göttingen he found three renowned mathematicians, Felix Klein, David Hilbert and Hermann Minkowski. Very soon after his arrival, Born formed close ties to the two men. Being class scribe put Born into regular, invaluable contact with Hilbert, Hilbert became Borns mentor after selecting him to be the first to hold the unpaid, semi-official position of assistant. Borns introduction to Minkowski came through Borns stepmother, Bertha, as she knew Minkowski from dancing classes in Königsberg, the introduction netted Born invitations to the Minkowski household for Sunday dinners. In addition, while performing his duties as scribe and assistant, Borns relationship with Klein was more problematic
12.
Emil Wolf
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He is also the author of several works on optics. Wolf was born in Prague, Czechoslovakia and he was forced to leave his native country when the Germans invaded, After brief periods in Italy and France, he came to the United Kingdom in 1940. He received his B. Sc. in Mathematics and Physics, between 1951 and 1954 he worked at the University of Edinburgh with Max Born, writing the famous textbook on Optics now usually known simply as Born and Wolf. After a period on the Faculty of the University of Manchester and he is currently the Wilson Professor of Optical Physics at the University of Rochester. He is a naturalized US citizen and he was president of the Optical Society of America in 1978. Wolf now resides in Cloverwood in Pittsford, New York, with his wife and he also predicted a new mechanism that produces redshift and blueshift, that is not due to moving sources, that has subsequently been confirmed experimentally. Technically, he found that two non-Lambertian sources that emit beamed energy, can interact in a way that causes a shift in the spectral lines. The Wolf Effect can produce either redshifts or blueshifts, depending on the point of view. A subsequent 1999 article by Sisir Roy et al. have suggested that the Wolf Effect may explain discordant redshift in certain quasars Ref. Wolf is a well known author in the field of optics. Along with Max Born, he co-wrote Principles of Optics of one of the textbooks of optics commonly known as Born. He also co-authored, along with Leonard Mandel, Optical Coherence and he is the author of Introduction to the Theory of Coherence and Polarization of Light and Selected Works of Emil Wolf with Commentary. He also edits the Progress in Optics series of books since its inception in 1962, frederic Ives Medal of the Optical Society of America Albert A. G. Past presidents of the Optical Society of America Progress in Optics Emil Wolf, home Page at University of Rochester. Principles of Optics, Electromagnetic Theory of Propagation, Interference and Diffraction of Light Sample chapters, Emil Wolf at the Mathematics Genealogy Project Articles Published by early OSA Presidents Journal of the Optical Society of America
13.
F. J. Duarte
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Francisco Javier Frank Duarte is a Chilean-born laser physicist and author/editor of several well-known books on tunable lasers and quantum optics. He introduced the generalized multiple-prism dispersion theory, has discovered various multiple-prism grating oscillator laser configurations, duartes research has mainly focused on physical and laser optics and has taken place at a number of institutions in the academic, industrial, and defense sectors. Duarte and Piper introduced the multiple-prism near-grazing-incidence grating cavities originally disclosed as copper-laser-pumped narrow-linewidth tunable laser oscillators and he then introduced multiple-prism grating configurations to high-power CO2 laser oscillators. Duarte also developed the theories for narrow-linewidth dispersive laser oscillators, and multiple-prism laser pulse compression, the tunable narrow-linewidth laser oscillator configurations, introduced by Duarte and Piper, were adopted by various research groups working on uranium atomic vapor laser isotope separation. This work was supported by the Australian Atomic Energy Commission, during the course of this research, Duarte writes that he did approach the then federal minister for energy, Sir John Carrick, to advocate for the introduction of an AVLIS facility in Australia. In 2002, he participated in research that led to the separation of lithium using narrow-linewidth tunable diode lasers. From the mid-1980s to early 1990s Duarte and scientists from the US Army Missile Command developed ruggedized narrow-linewidth laser oscillators tunable directly in the visible spectrum and this constituted the first disclosure, in the open literature, of a tunable narrow-linewidth laser tested on a rugged terrain. This research led to experimentation with polymer gain media and in 1994 Duarte reported on the first narrow-linewidth tunable solid state dye laser oscillators and these dispersive oscillator architectures were then refined to yield single-longitudinal-mode emission limited only by Heisenbergs uncertainty principle. In 2005, Duarte and colleagues were the first to demonstrate directional coherent emission from an electrically excited organic semiconductor and these experiments utilized a tandem OLED within an interferometric configuration. In the late 1980s, Duarte invented the N-slit laser interferometer and applied Dirac’s notation to describe quantum mechanically its interferometric, Duarte also derived the cavity linewidth equation, for dispersive laser oscillators, using quantum mechanical principles. More recently, Duarte and colleagues have developed very large N-slit laser interferometers to generate and propagate interferometric characters for secure free-space optical communications, interferometric characters is a term coined in 2002 to link interefometric signals to alphanumerical characters. Duarte provides a description of quantum optics, almost entirely via Diracs notation, in this book he derives the probability amplitude for quantum entanglement, | ψ ⟩ =12 which he calls the Pryce-Ward probability amplitude, from an N-slit interferometric perspective. Duarte also emphasizes a pragmatic approach to quantum mechanics. At Macquarie University, Duarte studied quantum physics under John Clive Ward and his PhD research was on laser physics and his supervisor was James A. Piper. In the area of university politics, he established and led the successful Macquarie science reform movement, macquaries science reform, was widely supported by local scientists including physicists R. E. Aitchison, R. E. B. Makinson, A. W. Pryor, and J. C. Ward, in 1980, Duarte was elected as one of the Macquarie representatives to the Australian Union of Students from where he was expelled, and then reinstated, for running over the tables. Following completion of his PhD work, Duarte did post doctoral research, with B. J. Orr at the University of New South Wales, in 1983, Duarte traveled to the United States to assume a physics professorship at the University of Alabama. In 1985 he joined the Imaging Research Laboratories, at the Eastman Kodak Company, while at Kodak he was chairman of Lasers 87 and subsequent conferences in this series
14.
Isaac Newton
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His book Philosophiæ Naturalis Principia Mathematica, first published in 1687, laid the foundations of classical mechanics. Newton also made contributions to optics, and he shares credit with Gottfried Wilhelm Leibniz for developing the infinitesimal calculus. Newtons Principia formulated the laws of motion and universal gravitation that dominated scientists view of the universe for the next three centuries. Newtons work on light was collected in his influential book Opticks. He also formulated a law of cooling, made the first theoretical calculation of the speed of sound. Newton was a fellow of Trinity College and the second Lucasian Professor of Mathematics at the University of Cambridge, politically and personally tied to the Whig party, Newton served two brief terms as Member of Parliament for the University of Cambridge, in 1689–90 and 1701–02. He was knighted by Queen Anne in 1705 and he spent the last three decades of his life in London, serving as Warden and Master of the Royal Mint and his father, also named Isaac Newton, had died three months before. Born prematurely, he was a child, his mother Hannah Ayscough reportedly said that he could have fit inside a quart mug. When Newton was three, his mother remarried and went to live with her new husband, the Reverend Barnabas Smith, leaving her son in the care of his maternal grandmother, Newtons mother had three children from her second marriage. From the age of twelve until he was seventeen, Newton was educated at The Kings School, Grantham which taught Latin and Greek. He was removed from school, and by October 1659, he was to be found at Woolsthorpe-by-Colsterworth, Henry Stokes, master at the Kings School, persuaded his mother to send him back to school so that he might complete his education. Motivated partly by a desire for revenge against a bully, he became the top-ranked student. In June 1661, he was admitted to Trinity College, Cambridge and he started as a subsizar—paying his way by performing valets duties—until he was awarded a scholarship in 1664, which guaranteed him four more years until he would get his M. A. He set down in his notebook a series of Quaestiones about mechanical philosophy as he found it, in 1665, he discovered the generalised binomial theorem and began to develop a mathematical theory that later became calculus. Soon after Newton had obtained his B. A. degree in August 1665, in April 1667, he returned to Cambridge and in October was elected as a fellow of Trinity. Fellows were required to become ordained priests, although this was not enforced in the restoration years, however, by 1675 the issue could not be avoided and by then his unconventional views stood in the way. Nevertheless, Newton managed to avoid it by means of a special permission from Charles II. A and he was elected a Fellow of the Royal Society in 1672. Newtons work has been said to distinctly advance every branch of mathematics then studied and his work on the subject usually referred to as fluxions or calculus, seen in a manuscript of October 1666, is now published among Newtons mathematical papers
15.
Crown glass (optics)
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Crown glass is a type of optical glass used in lenses and other optical components. It has relatively low refractive index and low dispersion, crown glass is produced from alkali-lime silicates containing approximately 10% potassium oxide and is one of the earliest low dispersion glasses. As well as the specific material named crown glass, there are other optical glasses with similar properties that are also called crown glasses, generally, this is any glass with Abbe numbers in the range 50 to 85. For example, the borosilicate glass Schott BK7 is a common crown glass. Borosilicates contain about 10% boric oxide, have good optical and mechanical characteristics, other additives used in crown glasses include zinc oxide, phosphorus pentoxide, barium oxide, fluorite and lanthanum oxide. A concave lens of flint glass is commonly combined with a lens of crown glass to produce an achromatic doublet. The dispersions of the glasses partially compensate for other, producing reduced chromatic aberration compared to a singlet lens with the same focal length
16.
Flint glass
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Flint glass is optical glass that has relatively high refractive index and low Abbe number. Flint glasses are arbitrarily defined as having an Abbe number of 50 to 55 or less, the currently known flint glasses have refractive indices ranging between 1.45 and 2.00. With respect to glass, the term flint derives from the flint nodules found in the deposits of southeast England that were used as a source of high purity silica by George Ravenscroft. 1662, to produce a lead glass that was the precursor to English lead crystal. Traditionally, flint glasses were lead glasses containing around 4–60% lead oxide, however, in many modern flint glasses, lead oxides are replaced with other metal oxides such as titanium dioxide and zirconium dioxide without significantly altering the optical properties of the glass. Crown glass Chromatic aberration Cup plate Kurkjian, Charles R. and Prindle, journal of the American Ceramic Society,81, 795-813
17.
Fused quartz
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Fused quartz or fused silica is glass consisting of silica in amorphous form. It differs from traditional glasses in containing no other ingredients, which are added to glass to lower the melt temperature. Fused silica, therefore, has high working and melting temperatures, the optical and thermal properties of fused quartz are superior to those of other types of glass due to its purity. For these reasons, it use in situations such as semiconductor fabrication. It has better ultraviolet transmission than most other glasses, and so is used to make lenses and its low coefficient of thermal expansion also makes it a useful material for precision mirror substrates. Fused quartz is produced by fusing high-purity silica sand, which consists of quartz crystals, quartz contains only silicon and oxygen, although commercial quartz glass often contains impurities. The most dominant impurities are aluminium and titanium, melting is effected at approximately 1650 °C using either an electrically heated furnace or a gas/oxygen-fuelled furnace. This results in a transparent glass with a purity and improved optical transmission in the deep ultraviolet. Fused quartz is normally transparent, the process of fusion results in a material that is translucent, the material can however appear opaque owing to the presence of small air bubbles trapped within the material. The water content is determined by the manufacturing process, flame fused material always has a higher water content due to the combination of the hydrocarbons and oxygen fuelling the furnace forming hydroxyl groups within the material. An IR grade material typically has an content of <10 parts per million, most of the applications of fused silica exploit its wide transparency range, which extends from the UV to the near IR. Fused silica is the key starting material for optical fiber, used for telecommunications, vacuum tubes with silica envelopes allowed for radiation cooling by incandescent anodes. Because of its strength fused silica was used in deep diving vessels such as the Bathysphere, the combination of strength, thermal stability, and UV transparency makes it an excellent substrate for projection masks for photolithography. EPROMs are recognizable by the transparent fused quartz window which sits on top of the package, through which the chip is visible. Due to the stability and composition it is used in semiconductor fabrication furnaces. Fused quartz has nearly ideal properties for fabricating first surface mirrors such as used in telescopes. The material behaves in a way and allows the optical fabricator to put a very smooth polish onto the surface and produce the desired figure with fewer testing iterations. These lenses are used for UV photography, as the glass has a lower extinction rate than lens made with more common flint or crown glass formulas
18.
Ultraviolet
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Ultraviolet is an electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation constitutes about 10% of the light output of the Sun. It is also produced by electric arcs and specialized lights, such as lamps, tanning lamps. Consequently, the effects of UV are greater than simple heating effects. Suntan, freckling and sunburn are familiar effects of over-exposure, along with risk of skin cancer. Living things on dry land would be damaged by ultraviolet radiation from the Sun if most of it were not filtered out by the Earths atmosphere. More-energetic, shorter-wavelength extreme UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground, Ultraviolet is also responsible for the formation of bone-strengthening vitamin D in most land vertebrates, including humans. The UV spectrum thus has both beneficial and harmful to human health. Ultraviolet rays are invisible to most humans, the lens in a human eye ordinarily filters out UVB frequencies or higher, and humans lack color receptor adaptations for ultraviolet rays. Under some conditions, children and young adults can see ultraviolet down to wavelengths of about 310 nm, near-UV radiation is visible to some insects, mammals, and birds. Small birds have a fourth color receptor for ultraviolet rays, this gives birds true UV vision, reindeer use near-UV radiation to see polar bears, who are poorly visible in regular light because they blend in with the snow. UV also allows mammals to see urine trails, which is helpful for animals to find food in the wild. The males and females of some species look identical to the human eye. Ultraviolet means beyond violet, violet being the color of the highest frequencies of visible light, Ultraviolet has a higher frequency than violet light. He called them oxidizing rays to emphasize chemical reactivity and to them from heat rays. The terms chemical and heat rays were eventually dropped in favour of ultraviolet and infrared radiation, in 1878 the effect of short-wavelength light on sterilizing bacteria was discovered. By 1903 it was known the most effective wavelengths were around 250 nm, in 1960, the effect of ultraviolet radiation on DNA was established. The discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet because it is absorbed by air, was made in 1893 by the German physicist Victor Schumann
19.
Infrared
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It extends from the nominal red edge of the visible spectrum at 700 nanometers, to 1000000 nm. Most of the radiation emitted by objects near room temperature is infrared. Like all EMR, IR carries radiant energy, and behaves both like a wave and like its quantum particle, the photon, slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has an effect on Earths climate. Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements and it excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines absorption and transmission of photons in the infrared range, Infrared radiation is used in industrial, scientific, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected, Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatuses. Thermal-infrared imaging is used extensively for military and civilian purposes, military applications include target acquisition, surveillance, night vision, homing, and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm, Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers to 1 mm. This range of wavelengths corresponds to a range of approximately 430 THz down to 300 GHz. Below infrared is the portion of the electromagnetic spectrum. Sunlight, at a temperature of 5,780 kelvins, is composed of near thermal-spectrum radiation that is slightly more than half infrared. At zenith, sunlight provides an irradiance of just over 1 kilowatt per square meter at sea level, of this energy,527 watts is infrared radiation,445 watts is visible light, and 32 watts is ultraviolet radiation. Nearly all the radiation in sunlight is near infrared, shorter than 4 micrometers. On the surface of Earth, at far lower temperatures than the surface of the Sun, almost all thermal radiation consists of infrared in mid-infrared region, much longer than in sunlight. Of these natural thermal radiation processes only lightning and natural fires are hot enough to produce much visible energy, thermal infrared radiation also has a maximum emission wavelength, which is inversely proportional to the absolute temperature of object, in accordance with Wiens displacement law. Therefore, the band is often subdivided into smaller sections. Due to the nature of the blackbody radiation curves, typical hot objects, such as exhaust pipes, the three regions are used for observation of different temperature ranges, and hence different environments in space
20.
Brewster's angle
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Brewsters angle is an angle of incidence at which light with a particular polarization is perfectly transmitted through a transparent dielectric surface, with no reflection. When unpolarized light is incident at this angle, the light that is reflected from the surface is therefore perfectly polarized and this special angle of incidence is named after the Scottish physicist Sir David Brewster. When light encounters a boundary between two media with different refractive indices, some of it is reflected as shown in the figure above. The fraction that is reflected is described by the Fresnel equations and this equation is known as Brewsters law, and the angle defined by it is Brewsters angle. The physical mechanism for this can be understood from the manner in which electric dipoles in the media respond to p-polarized light. One can imagine that light incident on the surface is absorbed, the polarization of freely propagating light is always perpendicular to the direction in which the light is travelling. The dipoles that produce the transmitted light oscillate in the direction of that light. These same oscillating dipoles also generate the reflected light, however, dipoles do not radiate any energy in the direction of the dipole moment. With simple geometry this condition can be expressed as θ1 + θ2 =90 ∘, solving for θB gives θ B = arctan. For a glass medium in air, Brewsters angle for light is approximately 56°, while for an air-water interface. Since the refractive index for a given medium changes depending on the wavelength of light, the phenomenon of light being polarized by reflection from a surface at a particular angle was first observed by Étienne-Louis Malus in 1808. He attempted to relate the polarizing angle to the index of the material. In 1815, Brewster experimented with higher-quality materials and showed that this angle was a function of the refractive index, the concept of a polarizing angle can be extended to the concept of a Brewster wavenumber to cover planar interfaces between two linear bianisotropic materials. In the case of reflection at Brewsters angle, the reflected and refracted rays are mutually perpendicular, for magnetic materials, Brewsters angle can exist for only one of the incident wave polarizations, as determined by the relative strengths of the dielectric permittivity and magnetic permeability. This has implications for the existence of generalized Brewster angles for dielectric metasurfaces, polarized sunglasses use the principle of Brewsters angle to reduce glare from the sun reflecting off horizontal surfaces such as water or road. In a large range of angles around Brewsters angle, the reflection of p-polarized light is lower than s-polarized light, thus, if the sun is low in the sky, reflected light is mostly s-polarized. Polarizing sunglasses use a material such as Polaroid sheets to block horizontally-polarized light. The effect is strongest with smooth surfaces such as water, but reflections from roads, photographers use the same principle to remove reflections from water so that they can photograph objects beneath the surface
21.
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
22.
Abbe prism
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In optics, an Abbe prism, named for its inventor, the German physicist Ernst Abbe, is a type of constant deviation dispersive prism similar to a Pellin–Broca prism. The prism consists of a block of glass forming a right prism with 30°–60°–90° triangular faces, when in use, a beam of light enters face AB, is refracted and undergoes total internal reflection from face BC, and is refracted again on exiting face AC. The prism is designed such that one wavelength of the light exits the prism at a deviation angle of exactly 60°. This is the minimum possible deviation of the prism, all other wavelengths being deviated by greater angles, by rotating the prism around any point O on the face AB, the wavelength which is deviated by 60° can be selected. The dispersive Abbe prism should not be confused with the non-dispersive Porro–Abbe or Abbe–Koenig prisms
23.
Amici prism
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An Amici prism, named for the astronomer Giovanni Amici, is a type of compound dispersive prism used in spectrometers. The Amici prism consists of two triangular prisms in contact, with the first typically being made from a crown glass. Light entering the first prism is refracted at the first air-glass interface, the prism angles and materials are chosen such that one wavelength of light, the centre wavelength, exits the prism parallel to the entrance beam. The prism assembly is thus a direct-vision prism, and is used as such in hand-held spectroscopes. Other wavelengths are deflected at angles depending on the dispersion of the materials. Looking at a light source through the prism thus shows the spectrum of the source. By 1860, Amici realized that one can join this type of prism back-to-back with a copy of itself. The exiting ray of the wavelength is thus not only undeviated from the incident ray. Amici himself never published about his nondeviating prism, but rather communicated the idea to his friend Donati, however, the dispersion of Amici prisms can be accurately calculated using the multiple-prism dispersion theory assuming no spatial separation between the prism components. The dispersive Amici prism should not be confused with the non-dispersive Amici roof prism
24.
Compound prism
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A compound prism is a set of multiple triangular prism elements placed in contact, and often cemented together to form a solid assembly. The use of elements gives several advantages to an optical designer. Thus, light at the wavelength which enters at an angle θ0 with respect to the optical axis. This kind of effect is called direct vision dispersion or nondeviating dispersion. One can achieve deviation of the incident beam while also reducing the dispersion introduced into the beam. This effect is used in beam steering, One can tune the prism dispersion to achieve greater dispersion linearity or to achieve higher-order dispersion effects. The simplest compound prism is a doublet, consisting of two elements in contact, as shown in the figure at right. A ray of light passing through the prism is refracted at the first air-glass interface, the deviation angle δ of the ray is given by the difference in ray angle between the incident ray and the exiting ray, δ = θ0 − θ4. While one can produce direct vision dispersion from doublet prisms, there is typically significant displacement of the beam, note that α i indicates that the prism is inverted. The central wavelength of the spectrum is denoted λ ¯, doublet prisms are often used for direct-vision dispersion. Note that this formula is accurate under the small angle approximation. While the doublet prism is the simplest compound prism type, the prism is much more common. This prism is a three-element system, in which the first, the design layout is thus symmetric about the plane passing through the center of its second element. Thus, we can derive the expressions for the angles using these linear equations. The double-Amici prism is a form of the more general triplet prism. Although triplet prisms are rarely found in systems, their added degrees of freedom beyond the double-Amici design allow for improved dispersion linearity
25.
Diffraction grating
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In optics, a diffraction grating is an optical component with a periodic structure, which splits and diffracts light into several beams travelling in different directions. The emerging coloration is a form of structural coloration, the directions of these beams depend on the spacing of the grating and the wavelength of the light so that the grating acts as the dispersive element. Because of this, gratings are used in monochromators and spectrometers. For practical applications, gratings generally have ridges or rulings on their surface rather than dark lines, such gratings can be either transmissive or reflective. Gratings which modulate the phase rather than the amplitude of the incident light are also produced, the principles of diffraction gratings were discovered by James Gregory, about a year after Newtons prism experiments, initially with items such as bird feathers. The first man-made diffraction grating was made around 1785 by Philadelphia inventor David Rittenhouse and this was similar to notable German physicist Joseph von Fraunhofers wire diffraction grating in 1821. Diffraction can create rainbow colors when illuminated by a wide spectrum light source, a grating has parallel lines, while a CD has a spiral of finely-spaced data tracks. Diffraction colors also appear when one looks at a point source through a translucent fine-pitch umbrella-fabric covering. Decorative patterned plastic films based on reflective grating patches are very inexpensive, the relationship between the grating spacing and the angles of the incident and diffracted beams of light is known as the grating equation. Gratings may be of the reflective or transmissive type, analogous to a mirror or lens, respectively. A grating has a mode, in which there is no diffraction. An idealised grating is considered here which is made up of a set of slits of spacing d, assuming a plane wave of monochromatic light of wavelength λ with normal incidence, each slit in the grating acts as a quasi point-source from which light propagates in all directions. After light interacts with the grating, the light is composed of the sum of interfering wave components emanating from each slit in the grating. At any given point in space through which diffracted light may pass, similarly, when the path difference is λ, the phases will add together and maxima will occur. Thus, when light is incident on the grating, the diffracted light will have maxima at angles θm given by. It is straightforward to show if a plane wave is incident at any arbitrary angle θi. When solved for the diffracted angle maxima, the equation is, please note that these equations assume that both sides of the grating are in contact with the same medium. The light that corresponds to direct transmission is called the zero order, the other maxima occur at angles which are represented by non-zero integers m
26.
Astronomical spectroscopy
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Astronomical spectroscopy is used to measure three major bands of radiation, visible spectrum, radio, and X-ray. While all spectroscopy looks at areas of the spectrum, different methods are required to acquire the signal depending on the frequency. Ozone and molecular oxygen absorb light with wavelengths under 300 nm, meaning that X-ray, radio signals have much longer wavelengths than optical signals, and require the use of antennas or radio dishes. Physicists have been looking at the solar spectrum since Isaac Newton first used a prism to observe the refractive properties of light. In the early 1800s Joseph von Fraunhofer used his skills as a maker to create very pure prisms. The resolution of a prism is limited by its size, a prism will provide a more detailed spectrum. This issue was resolved in the early 1900s with the development of high-quality reflection gratings by J. S, plaskett at the Dominion Observatory in Ottawa, Canada. By creating a blazed grating which utilizes a number of parallel mirrors. These new spectroscopes were more detailed than a prism, required less light, the limitation to a blazed grating is the width of the mirrors, which can only be ground a finite amount before focus is lost, the maximum is around 1000 lines/mm. In order to overcome this limitation holographic gratings were developed, volume phase holographic gratings use a thin film of dichromated gelatin on a glass surface, which is subsequently exposed to a wave pattern created by an interferometer. The holographic gratings can have up to 6000 lines/mm and can be up to twice as efficient in collecting light as blazed gratings, because they are sealed between two sheets of glass, the holographic gratings are very versatile, potentially lasting decades before needing replacement. Light dispersed by the grating or prism in a spectrograph can be recorded by a detector, historically, photographic plates were widely used to record spectra until electronic detectors were developed, and today optical spectrographs most often employ charge-coupled devices. The wavelength scale of a spectrum can be calibrated by observing the spectrum of emission lines of known wavelength from a gas-discharge lamp, radio astronomy was founded with the work of Karl Jansky in the early 1930s, while working for Bell Labs. He built an antenna to look at potential sources of interference for transatlantic radio transmissions. One of the sources of noise discovered came not from Earth, in 1942, JS Hey captured the suns radio frequency using military radar receivers. Radio spectroscopy started with the discovery of the 21-centimeter H I line in 1951, radio interferometry was pioneered in 1946, when Joseph Lade Pawsey, Ruby Payne-Scott and Lindsay McCready used a single antenna atop a sea cliff to observe 200 MHz solar radiation. Two incident beams, one directly from the sun and the other reflected from the sea surface, the first multi-receiver interferometer was built in the same year by Martin Ryle and Vonberg. In 1960, Ryle and Antony Hewish published the technique of aperture synthesis to analyze interferometer data, the aperture synthesis process, which involves autocorrelating and discrete Fourier transforming the incoming signal, recovers both the spatial and frequency variation in flux
27.
Total internal reflection
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Total internal reflection is the phenomenon which occurs when a propagated wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the side of the boundary and the incident angle is greater than the critical angle. The critical angle is the angle of incidence above which the internal reflection occurs. This is particularly common as a phenomenon, where light waves are involved. When a wave reaches a boundary between different materials with different refractive indices, the wave will in general be partially refracted at the boundary surface, and partially reflected. This can only occur when the wave in a medium with a refractive index reaches a boundary with a medium of lower refractive index. For example, it will occur with light reaching air from glass, Total internal reflection of light can be demonstrated using a semi-circular block of glass or plastic. A ray box shines a beam of light onto the glass medium. At the glass/air boundary of the surface, what happens will depend on the angle. If θc is the angle, then the following scenarios depict what will happen according to the size of the incident angle. If θ ≤ θc, the ray will split, some of the ray will reflect off the boundary and this is not total internal reflection. If θ > θc, the ray reflects from the boundary. This is called total internal reflection and this physical property makes optical fibers useful and prismatic binoculars possible. It is also what gives diamonds their distinctive sparkle, as diamond has a high refractive index. The critical angle is the angle of incidence for which the angle of refraction is 90°, the angle of incidence is measured with respect to the normal at the refractive boundary. Consider a light ray passing from glass into air, the light emanating from the interface is bent towards the glass. When the incident angle is increased sufficiently, the transmitted angle reaches 90 degrees and it is at this point no light is transmitted into air. The critical angle θ c is given by Snells law, n 1 sin θ i = n 2 sin θ t, rearranging Snells Law, we get incidence sin θ i = n 2 n 1 sin θ t
28.
Pink Floyd
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Pink Floyd were an English rock band formed in London. They achieved international acclaim with their progressive and psychedelic music, Pink Floyd were founded in 1965 by students Syd Barrett on guitar and lead vocals, Nick Mason on drums, Roger Waters on bass and vocals, and Richard Wright on keyboards and vocals. Guitarist David Gilmour joined in December 1967, Barrett left in April 1968 due to deteriorating mental health. Waters became the primary lyricist and conceptual leader, devising the concepts behind their albums The Dark Side of the Moon, Wish You Were Here, Animals, The Wall. The Dark Side of the Moon and The Wall became two of the albums of all time. Following creative tensions, Wright left Pink Floyd in 1979, followed by Waters in 1985, Gilmour and Mason continued as Pink Floyd, Wright rejoined them as a session musician and, later, a band member. The three produced two more albums—A Momentary Lapse of Reason and The Division Bell —and toured through 1994, Barrett died in 2006, and Wright in 2008. The final Pink Floyd studio album, The Endless River, was recorded without Waters, Pink Floyd were inducted into the American Rock and Roll Hall of Fame in 1996 and the UK Music Hall of Fame in 2005. By 2013, the band had more than 250 million records worldwide. Roger Waters met Nick Mason while they were both studying architecture at the London Polytechnic at Regent Street and they first played music together in a group formed by Keith Noble and Clive Metcalfe with Nobles sister Sheilagh. Richard Wright, an architecture student, joined later that year. Waters played lead guitar, Mason drums, and Wright rhythm guitar, the band performed at private functions and rehearsed in a tearoom in the basement of the Regent Street Polytechnic. They performed songs by the Searchers and material written by their manager and songwriter, Mason moved out after the 1964 academic year, and guitarist Bob Klose moved in during September 1964, prompting Waters switch to bass. Sigma 6 went through several names, including the Meggadeaths, the Abdabs and the Screaming Abdabs, Leonards Lodgers, in 1964, as Metcalfe and Noble left to form their own band, guitarist Syd Barrett joined Klose and Waters at Stanhope Gardens. Barrett, two younger, had moved to London in 1962 to study at the Camberwell College of Arts. Waters and Barrett were childhood friends, Waters had often visited Barrett, Noble and Metcalfe left the Tea Set in late 1963, and Klose introduced the band to singer Chris Dennis, a technician with the Royal Air Force. In December 1964, they secured their first recording time, at a studio in West Hampstead, through one of Wrights friends, Wright, who was taking a break from his studies, did not participate in the session. When the RAF assigned Dennis a post in Bahrain in early 1965, later that year, they became the resident band at the Countdown Club near Kensington High Street in London, where from late night until early morning they played three sets of 90 minutes each
29.
The Dark Side of the Moon
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The Dark Side of the Moon is the eighth album by English rock band Pink Floyd, released on 1 March 1973 by Harvest Records. It thematically explores conflict, greed, the passage of time, and mental illness, developed during live performances, an early version was premiered several months before recording began, new material was recorded in two sessions in 1972 and 1973 at Abbey Road in London. The group used some advanced recording techniques at the time, including multitrack recording, analogue synthesizers were prominent in several tracks, and snippets from recorded interviews with Pink Floyds road crew and others provided philosophical quotations throughout. Engineer Alan Parsons was responsible for many distinctively notable sonic aspects, the album was an immediate commercial and critical success, it topped the Billboard Top LPs & Tapes chart for a week and remained in the chart for 741 weeks from 1973 to 1988. With an estimated 45 million copies sold, it is Pink Floyds most commercially successful album and it has been remastered and re-released twice, and covered in its entirety by several other acts. It produced two singles, Money and Us and Them, and is the bands most popular album among fans and critics, following Meddle in 1971, Pink Floyd assembled for an upcoming tour of Britain, Japan and the United States in December of that year. Rehearsing in Broadhurst Gardens in London, there was the prospect of a new album. In a band meeting at drummer Nick Masons home in Camden, the band had explored a similar idea with 1969s The Man and The Journey. In an interview for Rolling Stone, guitarist David Gilmour said, I think we all thought –, There was definitely a feeling that the words were going to be very clear and specific. Generally, all four members agreed that Waters album concept unified by a theme was a good idea. The band rehearsed at a warehouse in London owned by The Rolling Stones and they also purchased extra equipment, which included new speakers, a PA system, a 28-track mixing desk with four quadraphonic outputs, and a custom-built lighting rig. However, after discovering that that title had already used by another band, Medicine Head. The new material premièred at The Dome in Brighton, on 20 January 1972, michael Wale of The Times described the piece as. It was so understanding and musically questioning. Derek Jewell of The Sunday Times wrote The ambition of the Floyds artistic intention is now vast. Melody Maker was, however, less enthusiastic, Musically, there were great ideas. However, the tour was praised by the public. The bands lengthy tour through Europe and North America gave them the opportunity to make improvements to the scale
30.
Multiple-prism dispersion theory
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The first description of multiple-prism arrays, and multiple-prism dispersion, was given by Newton in his book Opticks. Prism pair expanders were introduced by Brewster in 1813, a modern mathematical description of the single-prism dispersion was given by Born and Wolf in 1959. The generalized multiple-prism dispersion theory was introduced by Duarte and Piper in 1982, similarly, ϕ2, m is the exit angle and ψ2, m its corresponding angle of refraction. The two main equations give the first order dispersion for an array of m prisms at the surface of the mth prism. The plus sign in the term in parentheses refers to a positive dispersive configuration while the minus sign refers to a compensating configuration. The k factors are the corresponding beam expansions, and the H factors are additional geometrical quantities and it can also be seen that the dispersion of the mth prism depends on the dispersion of the previous prism. A comprehensive review on practical multiple-prism beam expanders and multiple-prism angular dispersion theory, including explicit, more recently, the generalized multiple-prism dispersion theory has been extended to include positive and negative refraction. Also, higher order phase derivatives have been derived using a Newtonian iterative approach and this extension of the theory enables the evaluation of the Nth higher derivative via an elegant mathematical framework. Applications include further refinements in the design of prism pulse compressors, although originally classical in origin, in 1992 it was shown that this laser cavity linewidth equation can also be derived from interferometric quantum principles. In practice, M can be as high as 100-200, in 1987 the multiple-prism angular dispersion theory was extended to provide explicit second order equations directly applicable to the design of prismatic pulse compressors. Beam expander Laser linewidth Multiple-prism grating laser oscillator Prism and Multiple-Prism Pulse Compression, Tutorial
31.
Light
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Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to light, which is visible to the human eye and is responsible for the sense of sight. Visible light is defined as having wavelengths in the range of 400–700 nanometres, or 4.00 × 10−7 to 7.00 × 10−7 m. This wavelength means a range of roughly 430–750 terahertz. The main source of light on Earth is the Sun, sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of photosynthesis provides virtually all the used by living things. Historically, another important source of light for humans has been fire, with the development of electric lights and power systems, electric lighting has effectively replaced firelight. Some species of animals generate their own light, a process called bioluminescence, for example, fireflies use light to locate mates, and vampire squids use it to hide themselves from prey. Visible light, as all types of electromagnetic radiation, is experimentally found to always move at this speed in a vacuum. In physics, the term sometimes refers to electromagnetic radiation of any wavelength. In this sense, gamma rays, X-rays, microwaves and radio waves are also light, like all types of light, visible light is emitted and absorbed in tiny packets called photons and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality, the study of light, known as optics, is an important research area in modern physics. Generally, EM radiation, or EMR, is classified by wavelength into radio, microwave, infrared, the behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths, when EMR interacts with single atoms and molecules, its behavior depends on the amount of energy per quantum it carries. There exist animals that are sensitive to various types of infrared, infrared sensing in snakes depends on a kind of natural thermal imaging, in which tiny packets of cellular water are raised in temperature by the infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detect it, above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nanometers and the internal lens below 400. Furthermore, the rods and cones located in the retina of the eye cannot detect the very short ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses are able to detect ultraviolet, by quantum photon-absorption mechanisms, various sources define visible light as narrowly as 420 to 680 to as broadly as 380 to 800 nm
