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Homework Help: Potential Difference

  1. Jun 8, 2008 #1


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    1. The problem statement, all variables and given/known data

    How would we find the potential difference given the frequency of the incident light and the kenetic energy of an the emitted electrons?

    2. Relevant equations

    E= hf-W
    V= w/q
    e= 1.602*10^-19

    3. The attempt at a solution

    Given: f= 7.4*10^15 Hz
    KE= 1.9eV
    Required: potential difference

    Solution: KE= 1.9eV * 1.602*10^ -19 J/eV = 3.0438*10^-19

    V= 3.0438*10^-19/ 1.602*10^ -19 = 1.9

    The answer is supossedd to be 2.7, I dont think I'm doing this the correct way.
  2. jcsd
  3. Jun 8, 2008 #2


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    Homework Helper

    The stopping potential would be 1.9V, not sure what p.d. they are asking for though.
  4. Jun 8, 2008 #3


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    Staff Emeritus
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    Homework Helper

    Use the 1st equation you wrote,

    E = hf - W

    To get W, you need to calculate E and hf.
  5. Jun 8, 2008 #4


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    Even when you do that, you wouldnt get 2.7..
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