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Name: Stu
Status: other
Grade: N/A
Location: N/A
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Date: 4/2/2005


Question:
All bodies with a temperature above absolute zero emit thermal radiation. The type of radiation emitted depends only on temperature of the object emitting the radiation. why does it only depend on only temperature?


Replies:
You have to be careful not to over generalize the statement. Not all radiation emitted by a body is necessarily dependent only on the temperature. Various gaseous discharge tubes can produce strong monochromatic light (and other electromagnetic frequencies -- A low pressure mercury lamp for example produces intense ultraviolet radiation at 254 nm.). The radiation you are referring to is called "black body radiation" -- an unfortunate historical name that is a bit confusing because the body need not be "black". The "reason" it depends upon only the temperature is that it is produced by the vibrations of oscillating electrical charges. What these oscillating charges are bound to --atoms, molecules, particles -- is not relevant. Richard Feynman's "Lectures on Physics" Vol I provides more details.

Vince Calder



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