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black body
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black body

In physics, a hypothetical object that completely absorbs all electromagnetic radiation striking it. It is also a perfect emitter of thermal radiation.

Although a black body is hypothetical, a practical approximation can be made by using a small hole in the wall of a constant-temperature enclosure. The radiation emitted by a black body is of all wavelengths, but with maximum radiation at a particular wavelength that depends on the body's temperature. As the temperature increases, the wavelength of maximum intensity becomes shorter (see Wien's displacement law). The total energy emitted at all wavelengths is proportional to the fourth power of the absolute temperature (see Stefan-Boltzmann law). Attempts to explain these facts failed until the development of quantum theory in 1900.



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? Mentioned in ? References in periodicals archive
 
Spectral responsivity measurements are used to calibrate the response of a filter radiometer, in turn used to estimate the temperature of a black-body radiator and hence provide the reference standard for spectral irradiance measurements.
Uncertainty propagation for NIST visible spectral standards by Gardner, James L. / Journal of Research of the National Institute of Standards and Technology
The theoretical calculations suggest that if black-body radiation were producing the liight, it should be a billion times stronger at the vents than in the cooler water above.
Light at the bottom of the ocean by Science News
Most importantly, the 1979 redefinition of the candela allows this to be an approach for the realization of a luminous intensity scale--quite a simplification from the previous requirement to use a platinum-point black-body source.
The candela and photometric and radiometric measurements by Parr, Albert C. / Journal of Research of the National Institute of Standards and Technology
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