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Is all observable light caused by electrons dropping to a lower discrete energy level while bound in an atom? If so, how can a continuum of frequencies be generated? Is the thermal radiation spectrum continuous, or is it a multitude of "close" discretes?

Qmechanic
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Silliq
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1 Answers1

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all observable light caused by electrons dropping to a lower discrete energy level

It isn't, all light (visible and not not) is caused by charged particles moving. In atoms they can, as you say, only move between between distinct energy levels and so give distinct frequencies of light.

But a charged particle moving with random thermal motion will change direction, any change in direction (or acceleration = same thing) of a charged particle will give off electromagnetic energy. With a complete range of different motions you get a complete range of frequencies = a thermal spectrum.

edit see What are the various physical mechanisms for energy transfer to the photon during blackbody emission especially Luboš Motl's answer for a more complete description (but possibly beyond what the OP asked)

Martin Beckett
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