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The photoelectric effect

  1. Apr 12, 2009 #1
    1. The problem statement, all variables and given/known data
    When monochromatic light is incident on a metla plate,electrons are emmited only when the frequency of light exceeds a certain frequency.
    Explain in terms of energy, why this threshold frequency exist and why photon theory of light provides a better explnation of the photorlrctric effect than a wave theory of light.


    2. Relevant equations
    none that i know of


    3. The attempt at a solution
    Its not really a solution but i have talked about energy levels and in atoms and things like that.
     
  2. jcsd
  3. Apr 12, 2009 #2

    Redbelly98

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    The equation for the energy of a photon would definitely be relevant.
     
  4. Apr 12, 2009 #3
    what E=hf or do you want the photoelectric equartion and how do either of them prove it
    fh=workfunction+Ek(max)
     
  5. Apr 12, 2009 #4

    Redbelly98

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    Yes, those equations.

    What can you say about Ek if hf is less than the work function?
     
  6. Apr 12, 2009 #5
    so what you are suggesting is me saying look at the formula it gives you proof?
    sorry but i am not sure that will fly
     
  7. Apr 12, 2009 #6

    Redbelly98

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    No, I'm not suggesting you say "look at the formula" as your answer. I'm suggesting that you should look at the formula and think about it before coming up with your answer. :smile:

    Ek(max) = hf - workfunction​

    What would hf < workfunction imply about Ek?
     
  8. Apr 12, 2009 #7
    I get that it says a minimum frequency is required and there is a maximum enrgy required but you have failed to prove this bit which is my hardest

     
  9. Apr 12, 2009 #8

    rock.freak667

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    Well if we use wave theory, then no matter the frequency, as long as the light supplies energy eventually, the electrons should gain enough energy to be emitted. But this doesn't occur in practice.
     
  10. Apr 12, 2009 #9
    oh my god thankyou i didnt know that and thats all i wanted to here that solves my whole problem.
     
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