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Homework Help: Regarding photoelectrics

  1. Oct 2, 2008 #1
    i hav problem solving this.. help please?

    The 1st excitation energy of hydrogen atom is 10.2eV
    calc the speed of the slowest electron that can excite a hydrogen atom..

    (electron charge/mass ratio e/m = 1.7 x 10^11 C kg-1)

    C(speed of light ) is 3 x 10^8 ms-1
    h(planks constant) is 6.6 x 10 ^ -34 Js

    thats all the given information

    the answer is 1.9 x 106ms-1
     
  2. jcsd
  3. Oct 2, 2008 #2

    Redbelly98

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    The kinetic energy of the electron gets transfered to the excitation energy of the hydrogen atom.

    Can you express that statement in an equation?

    p.s. Welcome to PF.
     
  4. Oct 3, 2008 #3
    er..

    hf = work function energy?

    1st excitation energy is work function energy?
    speed of the slowest electron is the hf oso = 1/2 mv^2?
     
  5. Oct 3, 2008 #4

    Redbelly98

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    You're half-way correct, since 1/2 m v^2 is the kinetic energy of the electron.

    What is the excitation energy of the atom?
     
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