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Is incandescence a purely quantum phenomenon?

  1. Dec 29, 2005 #1
    I just read this from Wikipedia:

    Incandescence occurs in light bulbs, because the filament resists electron flow. This excites electrons in the filament material to jump to a higher atomic orbital and thus subsequently release a photon when they fall back to their original orbits. Depending on the energy difference between the two orbits, the emitted photon is of a different wavelength.

    Which means that if the filament is made of tungsten, then only photons having an energy (wavelength) corresponding to the energy levels of the atoms of tungsten can be emitted. Then how can the observed continuous spectrum be explained?
     
  2. jcsd
  3. Dec 29, 2005 #2

    Danger

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    I'd be a bit leery of taking Wiki's word on this one. 'Incandescent' simply means that it's hot enough to radiate EM in the visible part of the spectrum. This is caused by the resistance of the filament, not orbital shifts of the electrons. It's not a quantum phenomenon so much as a straight electrical one. A typical household bulb runs at somewhere around 2,500° C., so it covers pretty much the whole visible section plus a lot of infrared.
    Electricity isn't even required for incandescence. If you've ever seen a farrier (blacksmith) at work, or a steel plant in operation, then you'll recognize the glow from material heated in another manner.
    Better double-check me on this, but I'm pretty sure you don't need to bring stimulated emission into it.
     
    Last edited: Dec 29, 2005
  4. Dec 29, 2005 #3

    ZapperZ

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    Danger is correct. The light being emitted is not due to atomic transition, but rather due to the vibrational spectrum. That, by definition, is related to heat. So you can get the same effect by heating it any way you like. Resistive heating is just one such way.

    Just another example why I never use Wikipedia to look up anything.

    Zz.
     
  5. Dec 30, 2005 #4
    I wouldn't discount it that much. It's a pretty good resource for most things when you need a quick answer.
     
  6. Dec 30, 2005 #5

    ZapperZ

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    Caveat Emptor..

    Zz.
     
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