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Brightness of light & light model

  1. May 23, 2009 #1
    I have been wondering
    1. We know that light has a wave-particle duality. Does the "light" here mean electromagnetic radiation, or just visible lights?

    2. If it EMR exhibits wave-particle duality, does that mean radio waves are transmitted in form of photons?

    3. and finally, I was reading through one of the posts and quoted:
    Isn't the brightness in visible light dependent on the number of photons the stream of light has? (not the amplitude)

    Thank you very much!
  2. jcsd
  3. May 23, 2009 #2


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    All electromagnetic radiation is made of photons, either small high energy ones in x-rays or long low energy ones in radio waves.

    In fact all matter has a wave-particle duality it's just that the wavelength depends on the momentum of the object. For real world objects like a tennis ball the momentum is large enough that the wavelength is very small - so we only see the effect with very small objects like photons and sub-atomic particles.

    [/QUOTE]Isn't the brightness in visible light dependent on the number of photons the stream of light has? [/QUOTE]
    It depends on the number of photons/sec. However brightness for something seen by your eye also depends on the wavelength since your eye is more sensitive to certain wavelengths (colors).
  4. May 24, 2009 #3
    Since the brightness is dependent of the number of photons per sec

    So the amplitude of the wave doesn't do anything?
  5. May 24, 2009 #4

    Andy Resnick

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    Photon number is non-conserved, so connecting the number of photons to the field amplitude is non-trivial. "Brightness", in addition, has a specific definition in radiometry that is different from how the term is being used here. "Intensity" or would be a better term.
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