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The Epic Interactive Encyclopedia 1998
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Epic Interactive Encyclopedia, The - 1998 Edition (1998)(Epic Marketing).iso
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B
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Black_body
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INFOTEXT
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1992-09-03
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19 lines
In physics, a hypothetical object that
completely absorbs all thermal (heat)
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
law). The total energy emitted at all
wavelengths is proportional to the fourth
power of the temperature (see Stefan's law).
Attempts to explain these facts failed until
the development of quantum theory in 1900.