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Planckian locus in the CIE 1931 chromaticity diagram. In physics and color science, the Planckian locus or black body locus is the path or locus that the color of an incandescent black body would take in a particular chromaticity space as the blackbody temperature changes.
Planck radiation has a maximum intensity at a wavelength that depends on the temperature of the body. For example, at room temperature (~ 300 K), a body emits thermal radiation that is mostly infrared and invisible. At higher temperatures the amount of infrared radiation increases and can be felt as heat, and more visible radiation is emitted ...
The Planckian locus on the MacAdam (u, v) chromaticity diagram. The normals are lines of equal correlated color temperature. The CIE 1960 color space ("CIE 1960 UCS", variously expanded Uniform Color Space, Uniform Color Scale, Uniform Chromaticity Scale, Uniform Chromaticity Space) is another name for the (u, v) chromaticity space devised by David MacAdam.
(In contrast with Balfour Stewart's, Kirchhoff's definition of his absorption ratio did not refer in particular to a lamp-black surface as the source of the incident radiation.) Thus the ratio E(T, i) / a(T, i) of emitting power to absorptivity is a dimensioned quantity, with the dimensions of emitting power, because a(T, i) is dimensionless.
The solid curve with dots on it, through the middle, is the Planckian locus, with the dots corresponding to a few select black-body temperatures that are indicated just above the x-axis. The figures on the right show the related chromaticity diagram. The outer curved boundary is the spectral locus, with wavelengths shown in nanometers. The ...
The Planckian locus is depicted on the CIE 1960 UCS, along with isotherms (lines of constant correlated color temperature) and representative illuminant coordinates By the time the D-series was formalized by the CIE, [ 12 ] a computation of the chromaticity ( x , y ) {\displaystyle (x,y)} for a particular isotherm was included. [ 13 ]
The even spacing of the isotherms on the locus implies that the mired scale is a better measure of perceptual color difference than the temperature scale. The notion of using Planckian radiators as a yardstick against which to judge other light sources is not new. [6]
A Nicholson model, showing a short part of protein backbone (white) with side chains (grey). Note the snipped stubs representing hydrogen atoms. A good example of composite models is the Nicholson approach, widely used from the late 1970s for building models of biological macromolecules.