An atomicspectralline refers to emission and absorption events in a gas in which math n 2 math is the density of atoms in the upper energy state for the line, and math n 1 math is the density of atoms in the lower energy state for the line. The emission of atomicline radiation at frequency ... processes occurring in the formation of an atomicspectralline. The three processes are referred ... strength associated with the particular atomicspectralline math B 12 frac 4 pi 2 e 2 m e h nu c ,f ... levels is released or absorbed in the process. The frequency math at which the spectralline ... dt math into solid angle math d Omega math . For atomicline radiation math epsilon frac h nu 4 pi ... of atomicline radiation may be described by an absorption coefficient math kappa math with units .... ref The above equations have ignored the influence of the spectralline shape. To be accurate, the above equations need to be multiplied by the normalized spectralline shape, in which case the units ... of the gas in which the spectralline occurs, including the local spectral radiance or, in some presentations, the local spectral radiant energy density . When that state is either one of strict thermodynamic ... A. others Brose, H. L. transl. author1 link Arnold Sommerfeld year 1923 title Atomic Structure and Spectral Lines url http books.google.com books about Atomic structure and spectral lines.html?id u1UmAAAAMAAJ ...No footnotes date September 2008 Image Spectral lines en.PNG thumb Emission lines and absorption lines compared to a continuous spectrum. In physics , one thinks of atomicspectralline s from two viewpoints. An emission line is formed when an electron makes a transition from a particular discrete energy ... at the wavelength associated with these photons. An absorption line is formed when an electron makes ... , Oxford University Press, New York, ISBN 0195034376. ref then the distribution of atomic states of excitation which includes math n 2 math and math n 1 math determines the rates of atomic ... more details
Atomicspectralline Bohr model Electron configuration Emission spectrum Spectrum analysis Fraunhofer ..., pointing east at around 3 or 4 pm i.e., Sun in the West on a clear day. A spectralline is a dark or bright line in an otherwise uniform and continuous optical spectrum spectrum , resulting .... Types of line spectra Spectral lines are the result of interaction between a quantum system usually atoms , but sometimes molecule s or atomic nucleus atomic nuclei and a single photon . When ... in an emission line. Spectral lines are highly atom specific, and can be used to identify the chemical ... detailed designations usually include the line wavelength and may include a multiplet number for atomic ... lines of atomic hydrogen also have designations within their respective Hydrogen spectral series series , such as the Lyman series or Balmer series . Spectralline broadening and shift A spectralline ... in the gas. Since the spectralline is a combination of all of the emitted radiation, the higher the temperature of the gas, the broader will be the spectralline emitted from that gas. This broadening ... isbn 0 521 45504 9 cite book first Hans R. last Griem year 1974 title SpectralLine Broadening ... Notes Reflist group note References reflist DEFAULTSORT SpectralLine Category Spectroscopy Category ... pl Linie spektralne pt Raia espectral ru simple Spectralline sk Spektr lna ...No footnotes date September 2008 Image Spectral lines continous.png thumb Continuous spectrum Image Spectral lines emission.png thumb Emission spectrum Emission lines Image Spectral lines absorption.png ..., either an emission line or an absorption line will be produced. Dark lines in a broad spectrum are produced ... one. This results in an absorption line , since the narrow frequency band of light initially ... . Several elements were discovered by spectroscopic means, such as helium , thallium , and cerium . Spectral ... spectral lines. Depending on the exact physical interaction with molecules, single particles, etc ... more details
Linespectral pairs LSP or linespectral frequencies LSF are used to represent linear predictive coding linear prediction coefficients LPC for transmission over a channel. LSPs have several properties e.g. smaller sensitivity to quantization noise that make them superior to direct quantization of LPCs. For this reason, LSPs are very useful in speech coding . Mathematical foundation The LP polynomial math A z 1 sum k 1 p a k z k math can be decomposed into math P z A z z p 1 A z 1 math math Q z A z z p 1 A z 1 math where P z corresponds to the vocal tract with the glottis closed and Q z with the glottis open. While A z has complex roots anywhere within the unit circle z transform , P z and Q z have the very useful property of only having roots on the unit circle, hence P is a palindromic polynomial and Q an antipalindromic polynomial . So to find them we take a test point math z exp jw math and evaluate math P exp jw math and math Q exp jw math using a grid of points between 0 and pi. The zeros roots of P z and Q z also happen to be interspersed which is why we swap coefficients as we find roots. So the process of finding the LSP frequencies is basically finding the roots of two polynomials of order p 1. The roots of P z and Q z occur in symmetrical pairs at w , hence the name Line Spectrum Pairs LSPs . Because all the roots are complex and two roots are found at 0 and math pi math , only p 2 roots need to be found for each polynomial. The output of the LSP search thus ... used for quantizing LPC filters. Linespectral frequencies can be interpolated. See also Log ... www.ece.mcgill.ca pkabal papers 1986 Kabal1986.pdf The Computation of LineSpectral Frequencies Using ... pdf lsp.pdf LineSpectral Pairs chapter as an online excerpt pdf Digital Signal Processing ... through it N times order of the filter , yielding the original filter, A z . Properties Linespectral pairs have several interesting and useful properties. When the roots of P z and Q z are interleaved ... more details
loss. Atomicline filters work via the absorption optics absorption or resonance Atomicspectralline lines of atomic vapors and so may also be designated an atomic resonance filter ARF . ref name gelbwachs1 Harvnb Gelbwachs 1988 p 1266 ref The three major types of atomicline filters are absorption ... near its atomicspectralline absorption lines by the Faraday effect and anomalous dispersion ... An atomicline filter ALF is an advanced optical filter optical band pass filter used in the physical ... atomicline filters the other two types are usually referred to specifically as Faraday filters or Voigt filters . Atomicline filters use different mechanisms and designs for different applications ... all other light. ref Harvnb Oehry Schupita Sumetsberger 1994 ref Atomicline filters can be considered ... systems. ref name hedin8 Harvnb Hedin 2002 p 8 ref Atomicline filters are superior to conventional ... of the atomicline filter was the infrared quantum counter , designed in the 1950s by Nicolaas ... for ALFs, many references use only the designation atomicline filter to describe specifically the absorption ... atomicline filter. ref name gelbwachs1 pumped how? Faraday filters, developed sometime before 1978, were a substantial improvement over absorption re emission atomicline filters of the time. ref name ... filters were being used for LIDAR. ref name kor Properties A technical definition of an atomicline ... an ALF generally has a passband on the order of 0.001 nanometer. That atomicline filters also ... rate The response time of an absorption re emission atomicline filter directly affects the rate information ... as the transmission spectrum of the FADOF. No optical losses are shown. Atomicline filters are inherently ... hedin33 Harvnb Hedin 2002 p 33 ref Band pass The band pass of an atomicline filter is usually equal ... For all of their efficiency, atomicline filters are not perfect there are many sources of error ... place. ref name gelbwachs4 Active atomicline filters are more likely to produce noise than ... more details
Wiktionary atomicAtomic may refer to Of or relating to the Atom , the smallest particle of a chemical element that retains its chemical properties Atomic Age , also known as the Atomic Era Atomic magazine Atomic magazine , an Australian computing and technology magazine Atomic Skis , an Austrian ski producer Atomic band , a Norwegian jazz quintet Atomic album Atomic album , an album by Lit Atomic song Atomic song , a song by Blondie Atomic , a song by Tiger Army from Tiger Army III Ghost Tigers Rise See also Atom disambiguation Atomicity database systems Nuclear disambiguation Atomism , philosophy about the basic building blocks of reality Atomic number , the number of protons found in the nucleus of an atom Atomic formula , a formula without subformulas Atomic Kitten , an English all female pop group Atomic Rooster , a British progressive rock band Atomic Coffee Machine , a 1950s Stovetop Coffee Machine Atomic chess , a chess variant Atomic operation , in computer science Atomic TV Nuclear weapon Nuclear power Atomic Dog , a song that is popular world wide written and performed by Our Father Who Art of Funk George Clinton from Parliament and the Funkadelics. disambiguation de Atomic fr Atomic it Atomic sk Atom rny ... more details
Unreferenced date April 2007 Spectral bands are part of optical spectra of polyatomic systems, including condensed materials, large molecules etc.. Each line corresponds to one level in the atom splits in the molecules. When the number of atoms is large, one gets a continuum of energy levels, the so called spectral bands . They are often labeled in the same way as the mono atomic lines. The bands may overlap. In general, the energy spectrum can be given by a density function, describing the number of energy levels of the quantum system for a given interval. Spectral bands have constant density, and when the bands overlap, the corresponding densities are added. Band spectra is the name given to a group of lines that are closely spaced and arranged in a regular sequence that appears to be a band. It is a colored band, separated by dark spaces on the two sides and arranged in a regular sequence. In one band, there are various sharp and wider color lines, that are closer on one side and wider on other. The intensity in each band falls off from definite limits and indistinct on the other side. In complete band spectra, there is a number lines in a band. This spectra is produced when the emitting substance is in the molecular state. Therefore they are also called molecular spectra. It is emitted by a molecule in vacuum tube , C arc core with metallic salt. The Band spectrum is the combination of many different spectrallinespectral lines , resulting from rotational, vibrational and Molecular electronic transition electronic transition . See also Band emission physics stub Categories Category Spectroscopy Interwikies de Spektralband fr Bande spectrale hr Spektroskopska vrpca ... more details
Unreferenced stub auto yes date December 2009 Spectral imaging is a branch of spectroscopy and of photography in which a complete spectrum or some spectral information such as the Doppler shift or Zeeman splitting of a spectralline is collected at every location in an image plane . Applications include astronomy , solar physics , analysis of Plasma physics plasmas in nuclear fusion experiments, planetology , and Earth remote sensing . Various distinctions among techniques are applied, based on criteria including spectral range, spectral resolution, number of bands, width and contiguousness of bands, and application. The terms include multispectral imaging , hyperspectral imaging , full spectral imaging , imaging spectroscopy or chemical imaging . These terms are seldom applied to the use of only Tetrachromacy four or Pentachromacy five bands that are all within the visible light range. Spectral images are often represented as an image cube, a type of data cube . See also Dopplergraph Imaging spectrometer DEFAULTSORT Spectral Imaging Category Astronomical spectroscopy Physics stub ar ... more details
Spectral analysis or Spectrum analysis may refer to Spectrum analysis in chemistry and physics, a method of analyzing the chemical properties of matter from bands in their visible spectrum Spectrum analyzer in signal processing , a device or algorithm that identifies a frequency domain representation of a time domain signal, typically by means of Fourier transform Spectral theory , in mathematics, a theory that extends eigenvalue s and eigenvector s to linear operators on Hilbert space , and more generally to the elements of a Banach algebra Spectral analysis in statistics, a procedure that decomposes a time series into a spectrum of cycles of different lengths. Spectral analysis is also known as frequency domain analysis In nuclear and particle physics, gamma spectroscopy , and high energy astronomy , the analysis of the output of a pulse height analyzer for characteristic features such as spectralline , edges, and various physical processes producing continuum shapes disambig ... more details
on the line of purples , which are various mixtures of violet and red light. See also Imaginary color DEFAULTSORT Spectral Color Category Color Color stub ar de Spektralfarbe eo Spektrokoloro ... more details
with Fourier analysis . The Fourier transform on the real line is in one sense the spectral theory ... discovery in quantum mechanics that spectral theory could explain features of atomic spectra was therefore fortuitous, rather than being an object of Hilbert s spectral theory. A definition of spectrum ...In mathematics , spectral theory is an inclusive term for theories extending the eigenvector and eigenvalue ... A short course on spectral theory author William Arveson chapter Chapter 1 spectral theory and Banach ... ref The theory is connected to that of analytic functions because the spectral properties of an operator are related to analytic functions of the spectral parameter. ref name Sadovnichi cite book ... space the spectral theory of operators url http books.google.com books?id SR1QkG6OkVEC&pg PA181 ... The name spectral theory was introduced by David Hilbert in his original formulation of Hilbert space theory, which was cast in terms of quadratic form s in infinitely many variables. The original spectral ... , in an infinite dimensional setting. The later discovery in quantum mechanics that spectral theory could explain features of Emission spectrum atomic spectra was therefore fortuitous. There have been three main ways to formulate spectral theory, all of which retain their usefulness. After Hilbert s initial formulation, the later development of abstract Hilbert space and the spectral theory of a single ... also study the spectral properties of operators on Banach spaces . For example, compact operator s on Banach spaces have many spectral properties similar to that of Matrix mathematics matrices . Physical ... ref Cquote Spectral theory is connected with the investigation of localized vibrations of a variety ... was made to atomic spectra a connection with the mathematical physics of vibration ... Cite book title Spectral Theory author Edgar Raymond Lorch year 2003 edition Reprint of Oxford 1962 ...&dq intitle spectral intitle theory inauthor Lorch&cd 1 ref Every eigenvalue of T belongs to T , but ... more details
Unreferenced date December 2009 The spectral linewidth characterizes the width of a spectralline , such as in the emission spectrum electromagnetic emission spectrum of an atom, or the frequency spectrum of an acoustic or electronic system. For example, the emission of an atom usually has a very thin spectral linewidth, as only transitions between discrete energy levels are allowed, leading to emission of photons with a certain energy. Several definitions are used to quantify the spectral linewidth, e.g. the full width at half maximum FWHM . While the spectral width of a resonator in electronics depends on the parameters of the components, and therefore can be easily adjusted over a wide range, linewidths are typically more difficult to adjust in physics. For example, even a resting atom which does not interact with its environment has a non zero linewidth , called the natural linewidth also called the decay width , which is a consequence of the Fourier transform Localization property Fourier transform limit classical description and the Heisenberg uncertainty principle quantum mechanical description . According to the uncertainty principle the uncertainty in energy, E , of a transition is inversely proportional to the lifetime, t of the excited state math Delta E Delta t gtrapprox frac hbar 2 . math In practice lines are further broadened by effects such as Doppler broadening . See also Bandwidth signal processing , a more generic term for a range of electromagnetic frequencies Q factor and linewidths in electronics, acoustics and optics Spectralline s in optics. This article also includes a list of sources of linewidth broadening. Spectral width in telecommunications Oscillator linewidth Laser linewidth DEFAULTSORT Spectral Linewidth Category Optics de Linienbreite lb Spektral Linnebreet ru tr Spektral izgi geni li i uk ... more details
, which produces a single number indicating the slope of the line of best fit through the spectral ...In astrophysics and planetary science , spectral slope , also called spectral gradient , is a measure of dependence of the reflectance on the wavelength . In digital signal processing , it is a measure of how quickly the spectrum of an audio sound tails off towards the high frequencies, calculated using a linear regression ref name Peeters04 G. Peeters, http recherche.ircam.fr equipes analyse synthese peeters ARTICLES Peeters 2003 cuidadoaudiofeatures.pdf A large set of audio features for sound description , tech. rep., IRCAM, 2004. ref . Image TheSpectralSlope.png thumb 300px right Illustration of the spectral slope Spectral slope in Astrophysics Planetary Science The visible and infrared electromagnetic spectrum spectrum of the reflected sunlight is used to infer physical and chemical properties of the surface of a body. Some objects are brighter reflect more in longer wavelengths red . Consequently, in visible light they will appear redder than objects showing no dependence of reflectance on the wavelength. The diagram illustrates three slopes a red slope , the reflectance is increasing with the wavelengths flat spectrum in black And a blue slope , the reflectance actually diminishing with the wavelengths The slope spectral gradient is defined as math S frac R F 1 R F 0 lambda 1 lambda 0 math where math R F 0 , R F 1 math is the reflectance measured with filters F sub 0 sub , F sub 1 sub having the central wavelengths sub 0 sub and sub 1 sub , respectively. ref name ArizonaBook Doressoundiram2007 Cite journal author A. Deressoundiram, H. Boehnhardt, S. Tegler and Chad ... spectrum appears flat in near infra red. Spectral slope in audio The spectral slope of many natural ... vs frequency include spectral rolloff , spectral centroid ref name Peeters04 . See also roll ... stub Signal processing stub fr Gradient spectral pt Gradiente espectral ... more details
A spectral glide is a modification of the vowel quality of a tone Erickson 1975, p. 72 . Since the vowel quality of a pitch music tone is determined by the overtone s, spectrum , or timbre all three terms being near equal of that tone, a spectral glide is a move from one spectrum characteristic of a vowel to another. A spectral glide may be accomplished through a wah wah music wah wah mute or pedal or through the modification of one s vocal tract while speaking, singing, or playing an instrument such as the didgeridoo . Buzzed lip instruments with large mouthpieces such as tuba and trombone allow extensive modification of vowel quality while woodwinds have a smaller range with the exception of the flute in air sound mode. Strings have the smallest range. ibid Important in the compositional use of spectral glides is the glide rate and the vowel contrasts used. Karlheinz Stockhausen specifies the use of a trumpet mute in his Punkte 1952 1962 64 66 93 through open and closed circles connected by a line. A. Wayne Slawson s computer generated Wishful Thinking about Winter Decca DL 710180 uses speechlike sounds featuring a large range of spectral glide rates. Loren Rush began investigating in 1967 the computer generated modeling of timbres in between familiar instruments such as a bassoon and bass clarinet and devised a program to provide a smooth transition between timbres. ibid, p. 73 Source Erickson, Robert 1975 . Sound Structure in Music . University of California Press. ISBN 0 520 02376 5. DEFAULTSORT Spectral Glide Category Musical performance techniques Category Vowels Category Timbre ... more details
modulation rate or line code pulse rate. Link spectral efficiency is typically used to analyse the efficiency of a digital modulation method or line code , sometimes in combination with a forward error ...Spectral efficiency , spectrum efficiency or bandwidth efficiency refers to the information rate that can ... protocol, and sometimes by the media access control the channel access protocol . Link spectral efficiency The link spectral efficiency of a digital communication system is measured in bit second ... or a data link . Alternatively, the spectral efficiency may be measured in bit symbol , which is equivalent ... of 3,400 300 3,100 hertz. The spectral efficiency or modulation efficiency is 56,000 3,100 18.1 ... efficiency measured in bit symbol or bpcu . In the case of baseband transmission line coding or pulse ... can not exceed 2 B symbols s in view to avoid intersymbol interference . Thus, the spectral efficiency ... 4 bit symbol or bpcu. Since QAM is a form of double sideband passband transmission, the spectral efficiency ... signal before passband filtering can be considered as baseband transmission, the spectral efficiency ..., a higher spectral efficiency is achieved if we consider the smaller passband bandwidth. If a forward error correction code is used, the spectral efficiency is reduced from the uncoded modulation efficiency ... that the encoder input bit rate is one half the encoder output rate, the spectral efficiency is 50 of the modulation efficiency. In exchange for this reduction in spectral efficiency, FEC usually reduces ... bound for the spectral efficiency possible without bit error s in a channel with a certain SNR ... 7 If the SNR is 1 times expressed as a ratio, corresponding to 0 decibel , the link spectral efficiency ... efficiently compressed. The link spectral efficiency of a wireless telephony link may ..., the link spectral efficiency can be somewhat misleading, as larger values are not necessarily more efficient in their overall use of radio spectrum. In a wireless network, high link spectral efficiency ... more details
In telecommunications , spectral component is any of the wave s that range outside the interval of frequency frequencies assigned to a signal. Any waveform can be disassembled into its spectral components by Fourier analysis or Fourier transformation . The length of a pulse thereby is determined by its complex spectral components, which include not just their relative intensities, but also the relative positions spectral phase of these spectral components. See also Spectral width Bandwidth limited pulse Category Telecommunications engineering Telecomm term stub ... more details
unreferenced date February 2008 In telecommunications , a spectral mask , also known as a channel mask or transmission mask, is a math ematically defined set of line mathematics lines applied to the levels of radio or optical transmission telecommunications transmission s. The spectral mask is generally intended to reduce adjacent channel interference by limiting excessive radiation at frequencies beyond the necessary bandwidth signal processing bandwidth . Attenuation of these spurious emission s is usually done with a band pass filter , Tuned filter tuned to allow through the correct center frequency of the carrier wave , as well as all necessary sideband s. The spectral mask is usually one of the things defined in a bandplan for each particular band radio band . It is essential in assuring that a transmission stays within its channel communications channel . An FM broadcasting FM radio station , for example, must attenuate everything beyond 75 kHz from the center frequency by a few decibel s, and anything beyond 100 kHz the channel boundary by much more. Emissions on further adjacent channel s must be reduced to almost zero. FM broadcasting FM broadcast subcarrier s are normally required to stay under 75 kHz and up to 100 kHz if attenuation reduced to comply with the mask. The introduction of in band on channel IBOC digital radio in the United States has been slowed down by issues concerning the subcarriers it uses &ndash and the corresponding increase in the amount of energy in the sidebands &ndash overstepping the bounds of the spectral mask set forth for FM by the National Radio Systems Committee NRSC and enforce d by the Federal Communications Commission FCC . Other types of modulation have different spectral masks for the same purpose. Many digital modulation methods such as OFDM use the electromagnetic spectrum very efficiently, allowing for a very tight spectral mask. This allows placement of broadcast stations or other transmissions on channels ... more details
orphan date December 2010 unreferenced date December 2010 Spectral purity is a quantification of the monochromaticity of a given light sample. This is a particularly important parameter in areas like laser operation and time measurement. Spectral purity is given by math Spectral purity frac triangle v v math Spectral purity is easier to achieve in devices that generate visible light visible and ultraviolet light, since higher frequency light results in greater spectral purity. Category Spectroscopy ... more details
Infobox VG image File Spectral Gene cover.jpg 250px developer Idea Factory publisher Idea Factory designer engine series Spectral released vgrelease JP December 13, 2007 genre Tactical role playing game SRPG modes Single player video game Single player ratings platforms PlayStation 2 Spectral Gene is an Tactical role playing game SRPG for the PlayStation 2 , and is the next installment in Idea Factory s Spectral series. It was developed and published for Japan by Idea Factory and was released on December 13, 2007. It is unknown if it will ever be published outside of Japan. ref http www.gamefaqs.com console ps2 data 941627.html Spectral Gene Info Spectral Gene Information Spectral Gene Release Date Bot generated title ref References Reflist External links ja icon http www.ideaf.co.jp spectral gene index.html The official website of Spectral Gene Category 2007 video games Category Tactical role playing video games Category PlayStation 2 games Category PlayStation 2 only games Category Video games developed in Japan Category Japan exclusive video games tactical rpg videogame stub ... more details
A spectral envelope is a curve in the frequency amplitude plane, derived from a Fourier magnitude spectrum. It describes one point in time one window, to be precise . nofootnotes date December 2010 one source date December 2010 In remote sensing using a spectrometer , the spectral envelope of a feature is the boundary of its electromagnetic spectrum spectral properties, as defined by the range of brightness levels in each of the spectral bands of interest. References Swartz, Diemo 1998 . Spectral Envelopes . http recherche.ircam.fr anasyn schwarz da specenv 3 3Spectral Envelopes.html . http www.unesco.org csi pub source rs15.htm Timbre Category Spectroscopy ... more details
In mathematics , the spectral abscissa of a matrix mathematics matrix or a bounded linear operator is the supremum among the real part of the elements in its spectrum of a matrix spectrum , sometines denoted as math eta A math Matrices Let sub 1 sub , ..., sub s sub be the real number real or complex number complex eigenvalues of a matrix A C sup n n sup . Then its spectral abscissa is defined as math eta A max i rm Re lambda i , math It is often used as a measure of stability in control theory, where a continuous system is stable iF all its eigenvalues are located in the left half plane, i.e. math eta A 0 math See also Spectral radius DEFAULTSORT Spectral Abscissa Category Spectral theory Category Matrix theory Linear algebra stub ... more details
In mathematics, the spectral gap is the difference between the absolute value moduli of the two largest eigenvalue s of a matrix or operator alternately, it is sometimes taken as the smallest non zero eigenvalue. Various theorems relate this difference to other properties of the system. See Expander graph discrete case Poincar inequality continuous case See also Spectral radius Eigengap disambig Category Mathematical disambiguation Category Spectral theory ... more details
cleanup date April 2011 lead too short date April 2011 Spectral Networks is deploying a WiMAX network in Southern Iowa and Northern Missouri . ref Reference 1 ref References ref cite web title Spectral Networks Website url http www.spectralnetworks.net publisher Source ref Reflist External links Spectral Networks http www.spectralnetworks.net Categories Category Articles created via the Article Wizard Category Telecommunications companies of the United States ... more details
In telecommunication s, spectral width is the wavelength interval over which the magnitude of all spectral component s is equal to or greater than a specified fraction of the magnitude of the component having the maximum value. In optical Telecommunication communications applications, the usual method of specifying spectral width is the full width at half maximum . This is the same convention used in Bandwidth signal processing bandwidth , defined as the frequency range where power drops by less than half at most &minus 3 dB . The FWHM method may be difficult to apply when the spectrum has a complex shape. Another method of specifying spectral width is a special case of Root mean square root mean square deviation where the independent variable is wavelength, , and f is a suitable radiometric quantity. The relative spectral width , , is frequently used where is obtained according to note 1, and is the center wavelength. See also Spectral linewidth in optics References Refimprove date January 2009 references FS1037C MS188 Category Telecommunications terms telecomm term stub fr Largeur de bande ... more details
In astronomy , the spectral index of a source is a measure of the dependence of radiative flux density on frequency . Given frequency math nu math and radiative flux math S math , the spectral index math alpha math is given implicitly by math S propto nu alpha. math Note that if flux does not follow a power law in frequency, the spectral index itself is a function of frequency. Rearranging the above, we see that the spectral index is given by math alpha left nu right frac partial log S left nu right partial log nu . math Spectral index is also sometimes defined in terms of wavelength math lambda math . In this case, the spectral index math alpha math is given implicitly by math S propto lambda alpha, math and at a given frequency, spectral index may be calculated by taking the derivative math alpha left lambda right frac partial log S left lambda right partial log lambda . math The opposite sign convention is sometimes employed, ref Burke, B.F., Graham Smith, F. 2009 . An Introduction to Radio Astronomy, 3rd Ed. , Cambridge University Press, Cambridge, UK, ISBN 9780521878081, page 132. ref in which the spectral index is given by math S propto nu alpha . math The spectral index of a source can hint at its properties. For example, using the positive sign convention, a spectral index of 0 to 2 at radio frequencies indicates thermal emission , while a steep negative spectral index typically indicates synchrotron emission . Spectral Index of Thermal emission At radio frequencies i.e. in the low frequency, long wavelength limit , where the Rayleigh Jeans law is a good approximation ... convention, the spectral index of thermal radiation is thus math alpha simeq 2 math in the Rayleigh Jeans regime. The spectral index departs from this value at shorter wavelengths, for which the Rayleigh ... regime, the radio spectral index is defined implicitly by ref cite web title Radio Spectral Index ... stub es ndice espectral fr Indice spectral it Indice spettrale ... more details
Unreferenced stub auto yes date December 2009 File Spectrum of blue sky.svg thumb 300px right Spectrum of blue sky Spectral Signatures are the specific combination of reflected and absorbed electromagnetic radiation electromagnetic EM radiation at varying wavelengths which can uniquely identify an object. The spectral signature of stars indicates the spectrum according to the EM spectrum. The spectral signature of an object is a function of the incidental EM wavelength and material interaction with that section of the electromagnetic spectrum . The measurements can be made with various instruments, including a task specific spectrometer , although the most common method is separation of the Red, Green, Blue and Near Infrared portion of the EM spectrum as acquired by digital cameras. Calibration of spectral signatures under specific illumination are collected in order to apply an empirical correction to airborne or satellite imagery digital images. When using a spectrometer, you will look through it at a tube of gas with high voltages passing through it. In the Spectrometer, you will be able to see specific rays of colour falling on graduations on the inside. Each substance will have its own unique falling of rays. Most remote sensing applications process digital images to extract spectral signature at each pixel and use such signature to divide the image in groups of similar pixels Segmentation image processing segmentation using different approaches, and, as last step, assign a class to each group classification by comparing with known spectral signatures. Depending on pixel resolution, a pixel can represent many spectral signature mixed together that is why a lot of remote sensing analysis is done to unmix mixtures . Ultimately correct matching of spectral signature recorded by image pixel with spectral signature of existing elements leads to accurate classification in remote sensing. DEFAULTSORT Spectral Signature Category Spectroscopy Sci stub ca Signatura espec ... more details
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