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Photoelectric Effect and ozone layer

  1. Oct 27, 2007 #1
    Hi. I hope someone can help. Here is the problem:

    [Pennies are made of zinc coated with copper. Copper has a work function of 4.7eV. The ozone layer blocks nearly all solar radiation with wavelength shorter than 320nm, but a very small amount of 200nm light still manages to reach the Earth's surface. Can direct sunlight produce photoelectrons from a penny?]

    I converted the 4.7eV into joules: 4.7eV * 1.602e-19J = 7.529e-19J
    I found the minimum kinetic energy needed to for the electrons to escape from the copper:
    KE = e * V_o => 1.602e-19 * 7.529e-19 = 1.206e-37J

    I'm thinking that I need to use the 200nm to find out whether the kinetic energy I calculated will be produced by the sunlight, but I don't see how to do that.
     
  2. jcsd
  3. Oct 27, 2007 #2

    Chi Meson

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    Your reasoning is incorrect. KE = E - W (E is energy per photon, W is work function, KE is max kinetic energy of photoelectron).

    Stay in eV, it's easier. Use 4.14 x 10^-15 eVs as h.

    Energy per photon is hf =hc/wavelength.

    How much energy in a 200 nm photon?
     
    Last edited: Oct 27, 2007
  4. Oct 27, 2007 #3
    Thank you!
     
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