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Homework Help: Kinetic energy of an ionized electron

  1. Apr 17, 2010 #1
    1. Ultraviolet light with a wavelength of 60.0 nm shines on a gas of hydrogen atoms in their ground states. Some of the atoms are ionized by the light. What is the kinetic energy of the electrons that are freed in this process?

    2. En = n2h2/8mL2

    3. To get L, I solved lambda = 2L/n with n = 1, obtaining L = 3*10-8 m. Plugging to the En equation, using n =1 and h = 4.14*10-15 eVs, I obtain an incorrect answer. I tried using both the Js and EvS numbers for h, but I was wrong either way...
  2. jcsd
  3. Apr 17, 2010 #2


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    The energy of a hydrogen atom is not the same as the energy of an infinite square well...

    But that doesn't matter.

    What you want to see is how much of the energy of the photon goes to ionizing the electron? (Hint: consider what the energy of an electron in the ground state of hydrogen is) Therefore, how much energy is left to give to the kinetic energy of the electron?
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