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Photon reflection from a metal surface

  1. Apr 9, 2010 #1

    I have been looking for a better explanation of the following question in different threads, but although there are some related question, I haven't found one that answers my question.

    I have read in Atkins-Physical chemistry book the following (summarized) explanation about why metal surfaces are shiny:

    "In an idealized metallic conductor, the absorption of light can excite electrons form the occupied levels to unoccupied. There is a near continuum of unoccupied energy levels, so the absorption is over a wide range of frequencies. The absorbed energy can be re-emitted very efficiently as light, which accounts for the shiny appearance of the metal surface."

    What bugs me is that if this is true, why when the electrons are excited by the absorption of the photon, they re-emit exactly with the same wavelength. If there is a continuum of energy levels, isn't it possible that the emitted photon would have different energy?

    I would appreciate any help. Thanks!
  2. jcsd
  3. Apr 11, 2010 #2
    Since there is a continuum of energy levels, the electrons are basically free. They get excited and then return to their ground state emitting the photon of same wavelength as it absorbed. To emit a photon of lesser energy (higher wavelength), there should be some intermediate state of higher lifetime. This is not the case with metals. Hence the emitted photon cannot have other energies.
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