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Homework Help: Finding Work function and Plank constant

  1. Jan 22, 2013 #1
    1. The problem statement, all variables and given/known data

    In experiments on lithium, Millikan observed a maximum
    kinetic energy of 0.550eV when electrons were ejected with 433.9nm light. When 253.5nm light was
    used, he observed a maximum kinetic energy of 2.57eV. Using these results find
    a) the work function for lithium, and
    b) the predicted value of Planck’s constant.

    2. Relevant equations
    h f = work function + kin_max

    3. The attempt at a solution

    for finding work function

    since work function=( h c)/ wavlenght

    so we know c , the speed of light , wavelenght, and plank constant so we can find it

    however b) ask us to find plank constant , we confuses me
  2. jcsd
  3. Jan 22, 2013 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Use that formula twice. You're given two sets of max energy and corresponding wavelength. 2 equations, 2 unknowns (work fn and h).
  4. Jan 22, 2013 #3
    Thank you , I just realized that
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