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Homework Help: Relating Work Function and Wavelength

  1. Dec 11, 2008 #1
    1. The problem statement, all variables and given/known data
    Barium has a work function of 2.48 eV. What is the longest wavelength of light that will cause electrons to be emitted from barium?

    2. Relevant equations
    W = hf○
    hf = W + Ek
    E = hf = hc/λ

    3. The attempt at a solution
    1 eV/1.6e-19 C = 2.48/X
    X = 3.97e-19

    f=5.99e14 Hz

    Now I'm lost...Anybody care to help? :)
  2. jcsd
  3. Dec 11, 2008 #2


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    Homework Helper

    So what's the relationship between frequency and wavelength? You've already used it (look at equation 3).
  4. Dec 11, 2008 #3
    I think I've figured out the problem using v=fλ, 3.0e8 = 5.98e14λ, λ=5.02e-7m.

    Also the answer to your question is that as frequency increases, wavelength decreases.

    Would be awesome if you could tell me I'm on the right track, and of course if I'm not, as well.
  5. Dec 11, 2008 #4


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    Homework Helper

    Yes, you are right.
  6. Dec 11, 2008 #5
    Thanks much.
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