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What produces the photons in light bulb filament?

  1. Nov 9, 2013 #1
    What produces the photons in light bulb filament? I know that electrons are emmitted by thermionic emmission from the filament . . . do they then fall back into the filament and emit EM radiation as they de-accellerate into the filament?
     
  2. jcsd
  3. Nov 9, 2013 #2

    mathman

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  4. Nov 9, 2013 #3
    Nice thanks. Here's the except with the explanation:

    "As these free electron move through the filament at high speeds they are constantly bumping into the atoms that make up the filament, the impact energy vibrating and heating these atoms. Bounded electrons in the atoms of the filament are temporarily boosted to a higher energy level. When the electron returns to its original energy level they release the extra energy in the form of photons. Metal atoms release primarily infrared light photons which happen to be invisible to the human eye, but if heated to a high enough temperature (around 2,200 C) will emit the visible light seen from a bulb. "

    I wonder now though why it's a nice continuum of EM radiation, rather than discrete lines of radiation we usually see. . .
     
  5. Nov 9, 2013 #4

    CWatters

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    I might be wrong but...

    In a solid I believe the energy levels form bands rather than discrete levels. So you get a near continuous spectrum of radiation (Black body)

    In a gas lamp the energy levels are discrete so you get characteristic emission lines.
     
  6. Nov 9, 2013 #5

    CWatters

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    http://www.asdi.com/getmedia/05be99...CTRAL-SIGNATURES-OF-NIGHTTIME-LIGHTS.pdf.aspx

    Conclusion
    We found substantial variation in the emission spectra of lighting types. Lamps that produce
    light through heat (incandescent, quartz halogens, and fuel lamps) emit primarily like blackbodies, with
    peak emission in the near infrared and emissions higher in the red than green and blue. Fluorescent,
    metal halide, high pressure and low pressure sodium lamps are gas discharge lamps, which emit
    different series of narrow emission lines. The identity of the gas discharge lamps can be discerned
    based on the wavelength positions of the emission lines...

    continues
     
  7. Aug 20, 2015 #6
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