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Quick question about PhotoElectric Effect

  1. Sep 10, 2013 #1
    1. The problem statement, all variables and given/known data
    I am wondering, what happens to those photons ( all having same energy level) in a light beam when the photons don't have enough energy to release the electrons in the metal that are more tightly attracted?
    Does the overall work function of the material decrease?


    2. Relevant equations

    KE= h*f- Workfunction

    3. The attempt at a solution

    At first glance, the eletrons in the material should become lessly attracted than before because when a light beam shines at an area, the temperature of that area increase.
    However, there's a rule that states that frequency below the lowest frequency of the light beam will not release the ANY electron no matter how long you shine the beam. So base on this, the electrons shouldn't become less attracted.

    But still, what happen to those electrons that don't have eneough energy to expell the electrons?
     
  2. jcsd
  3. Sep 11, 2013 #2

    ehild

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    Gold Member

    When the photon interacts with a free electron , but the energy is not enough to free the electron from the metal, the electron gains kinetic energy, so it will do its random motion inside the metal with higher speed. The electron collides with the vibrating atoms, imperfections or other electrons, and either re-radiates its extra energy as a photon (that is, part of the incident light is reflected) or transfers it to the vibrating atoms or to other electrons, so its extra energy is transferred to the whole metal. The metal becomes a bit warmer, then its transfers heat to the surroundings. So the energy of the absorbed photon will "heat up" the Universe at the end.

    ehild
     
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