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Homework Help: Excitation of an electron by a photon

  1. Dec 30, 2007 #1
    Hi, I had a question regarding excitation. If a photon is absorbed by an electron, and some of the energy is gained by the electron, which then moves to a higher energy level, what happens to the rest of the photon's energy - is a photon of lower energy, corresponding to the difference in energy gained by the electron and energy of photon emitted?

    For example, in the case of a hydrogen atom, the ground state is -13.6eV, the second energy level -3.4eV, and the third -1.5eV.

    If a photon of 11.5eV collides with an orbiting electron in the ground state, the electron will use 10.2eV of this, and be promoted to energy level 2; it however doesn't have enough energy to get to energy level 3. Is a photon, therefore of energy 11.5-10.2= 1.3eV emitted?

    Thanks for any help.
    Last edited: Dec 30, 2007
  2. jcsd
  3. Dec 30, 2007 #2


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    Yes. You can also think of it as an elastic collision which changes the energy of the incoming photon.
  4. Jan 7, 2008 #3
    Thanks for clearing that up.
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