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Mathematically, for the spectral power distribution of a radiant exitance or irradiance one may write: =where M(λ) is the spectral irradiance (or exitance) of the light (SI units: W/m 2 = kg·m −1 ·s −3); Φ is the radiant flux of the source (SI unit: watt, W); A is the area over which the radiant flux is integrated (SI unit: square meter, m 2); and λ is the wavelength (SI unit: meter, m).
The SED of M51 (upper right) obtained by combining data at many different wavelengths, e.g. UV, visible, and infrared (left). A spectral energy distribution (SED) is a plot of energy versus frequency or wavelength of light (not to be confused with a 'spectrum' of flux density vs frequency or wavelength). [1]
In the physical sciences, the term spectrum was introduced first into optics by Isaac Newton in the 17th century, referring to the range of colors observed when white light was dispersed through a prism. [1] [2] Soon the term referred to a plot of light intensity or power as a function of frequency or wavelength, also known as a spectral ...
A rainbow is a decomposition of white light into all of the spectral colors. Laser beams are monochromatic light, thereby exhibiting spectral colors. A spectral color is a color that is evoked by monochromatic light, i.e. either a spectral line with a single wavelength or frequency of light in the visible spectrum, or a relatively narrow spectral band (e.g. lasers).
Relative spectral power distributions (SPDs) of CIE illuminants A, B, and C from 380 nm to 780 nm. A standard illuminant is a theoretical source of visible light with a spectral power distribution that is published. Standard illuminants provide a basis for comparing images or colors recorded under different lighting.
A classic example is the automobile industry: the colorants used for interior fabrics, plastics and paints may be chosen to provide a good color match under a cool white fluorescent source, but the matches can disappear under different light sources (e.g. daylight or tungsten source). Furthermore, because of the differences in colorants ...
For example, if JE(λ) is spectral radiance with the unit W/m 2 /sr/m, then the quantal equivalent JQ(λ) characterizes that radiation with the unit photons/s/m 2 /sr/m. If CE λi ( λ ) ( i =1,2,3) are the three energy-based color matching functions for a particular color space (LMS color space for the purposes of this article), then the ...
The upper half of this diagram shows the frequency spectrum of a modern switching power supply which employs spread spectrum. The lower half is a waterfall plot showing the variation of the frequency spectrum over time during the power supply's heating up period. Spectrogram and 3 styles of waterfall plot of a whistled sequence of 3 notes vs time