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Homework Help: Photoelectric Effect and stopping potential

  1. Sep 9, 2013 #1
    1. The problem statement, all variables and given/known data

    When 445 nm light strikes a certain metal surface, the stopping potential is 70% of that which results when 410 nm light strikes the same metal.

    2. Relevant equations

    3. The attempt at a solution

    $$P=0.7P'\\ \frac { nE }{ t } =\frac { 0.7nE' }{ t } \\ \frac { hc }{ λ } =\frac { 0.7hc }{ λ' } \\ \frac { λ' }{ λ } =0.7$$
  2. jcsd
  3. Sep 9, 2013 #2
    And the question is???
    Oh and you are neglecting the work function of the metal- I think
  4. Sep 11, 2013 #3
    Opps. I didn't realize the question was cut off.

    Here's the second part:

    Based on this information and the table given in the textbook, identify the metal.

    Basically, what is required is to calculate the work function.

    A: work function 2.23 eV. Potassium.
  5. Sep 14, 2013 #4
    Show your effort please. As suggested, did you take the work function into account? Retry the problem.
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