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Origin of the fresnel effect

  1. Nov 11, 2008 #1
    I work in computer graphics so I use and am familiar with the fresnel equations governing reflections from conductors and dielectrics. My question is about the origin of these effects. As I understand it, the fresnel equations describe the 'average' result of myriad individual photon-material interactions, so what decides (at a quantum level I guess) whether an individual photon is reflected, transmitted or absorbed?

    Also am I right in thinking that each photon 'carries' a particular frequency of light with it, such that a particular colour of light is generated by the number of photons with each different frequency?
  2. jcsd
  3. Nov 11, 2008 #2

    What decides the fate of an individual photon is chance. [Of course, is photons impinge on surfaces with different properties, some have better chances than others]

    This is the modern view of quantum mechanics. The subject was heavily debated for the first half-century of QM, but now consensus is (almost) universal. Some very convincing experiments tell that only chance decides - there can be no "hidden parameter" unknown to us but attached to the particle that decides its fate.

    Keywords : EPR Einstein Podolsky Rosen, and also Alain Aspect and several more.
  4. Nov 11, 2008 #3
    ok sure I know that it's chance, I'm asking what decides the probabilities that go into the "dice roll"
  5. Nov 11, 2008 #4


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    The Fresnel equations follow from the boundary condition on the E,D,,B,H fields of a classical EM wave. This is treated in most advanced EM texts, and many optical texts.
    For a single photon, the resulting reflection and transmission coefficients are probabilities for reflection and transmission of a single photon.

    You are right about each photon carrying a particular frequency.
  6. Nov 12, 2008 #5
    Ok, thanks, but that's a little opaque. Is there any way to understand it in physical terms? What is it about the fact that metals conduct electricity that causes them to absorb a large part of the spectrum while dielectrics absorb very little?
  7. Nov 12, 2008 #6
    It is a solid state matter...

    have you ever heard about conduction bands or something like this?

    see Bloch and Fermi theory of bands. It is a quantum mechenical thoeory that can asnwer your questions about metals and dieletric.

    About the photons:

    yes they, as all the particles, have a frequencies... but it is not well known since you hit with heisenberg principle...what you actually see in experiments are distributions of frequanciese spread over a range ;)


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