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Optics from a Quantum Mechanical stand point

  1. Jun 18, 2014 #1
    I've tried looking this up online, but people only ever talk about the basic principles and formulas involved instead of the concepts behind it. My question is this: "What is happening at a quantum level when light is refracted or reflected?" How does the light interact with the atoms of medium "x" (as it moves between media of differing refractive indicies) that causes it to behave in such a way. I appreciate your insight in advanced!
  2. jcsd
  3. Jun 18, 2014 #2


    Staff: Mentor

    See the FAQ:
    https://www.physicsforums.com/showthread.php?t=511177 [Broken]

    Last edited by a moderator: May 6, 2017
  4. Jun 18, 2014 #3
    So I need to think of the photons as waves interacting with waves (phonons)? Here's where I'm at:

    Photons interact with matter (in this case) as a wave.
    The matter has a collective excited state known as a phonon that also behaves as a wave.
    Lower energy photons are repelled by the phonons (somehow?).
    Like energy photons are absorbed like canceling waveforms.
    Higher engery photons pass through the material, but are refracted through a kind of wave interference.

    How wrong am I?
    Last edited: Jun 18, 2014
  5. Jun 18, 2014 #4
    I like the following description of it: Hagan course notes

    It's from a course, and chapter 1 has a fairly intuitive walk-through of the origins of the refractive index which I think you'll find useful.
  6. Jun 18, 2014 #5


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    Phonons are more important in the infrared region. In visual optics, electronic excitations are much more important.
    It is often helpful to think of the atoms or molecules making up a solid as little electric dipoles. These will experience the electric field of the incident wave and will start to oscillate, thereby producing a changing electromagnetic field themselves. This scattered field overlaps with the incident field and gives rise to the refracted wave.
  7. Jun 18, 2014 #6

    Umm, that's a broken link, and in Swedish ha ha! X)
  8. Jun 18, 2014 #7
    That's strange, the link works for me (even now clicking it from your quoted post). Maybe try this instead, which is to the course page. The first link on that page should be to the pdf that I tried to link before.
  9. Jun 18, 2014 #8

    Okay, that one worked, thanks :)
    I suppose I should brush up on my nonexistent knowledge of field theory then
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