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Homework Help: The concept of Light

  1. Jul 14, 2013 #1
    Greetings. I am in part-time studies for my undergraduate I am taking physics for the first time.

    I am completely overwhelmed and am having a hard time of finding answers to the textbook questions in the textbook itself. The current question I am stumped in is:

    Suppose zinc is illuminated with ultraviolet light of a single frequency, for example. f= 1.5f threshold. Why might some electrons emerge with less energy than "maximum energy of electron after escape?"

    I appreciate any help and or guidance.

  2. jcsd
  3. Jul 14, 2013 #2
    Einstein's Photoelectric equation is

    KE ≤ E - W0

    Where the equality holds only for surface electrons. For the nonsurface electrons KE < E - W0.
  4. Jul 14, 2013 #3


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    The electrons in the metal do not all have the same energy.
    Does that help?

    @darkxponent: There are no "surface electrons" in the way you describe them.
  5. Jul 14, 2013 #4
    So in what way do i describe surface electrons? I studied them this way only, that the electrons at the surface need least energy to be separated because there potential energy less negative than any other electron.
  6. Jul 14, 2013 #5
    I appreciate the quick response. Can you give me an example or a bit more info so that I can fully understand (if you have time).
  7. Jul 14, 2013 #6


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    The relevant energy levels of electrons in metals all correspond to delocalized electrons. Their different energy levels just come from their different momentum and some additional quantum mechanics (band structure).

    @BRIX: Simple example: There are some electrons which need 1 eV of energy to get released, some electrons which need 2 eV, electrons which need some energy between that and so on. If you give all those electrons the same energy, they will have different energies afterwards (the same difference as before).
  8. Jul 14, 2013 #7
    Thank you!
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