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Homework Help: Photoelectric Effect and electrostatic potential

  1. Jan 29, 2008 #1


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    1. The problem statement, all variables and given/known data
    A silver ball is suspended by an insulating string in a vacuum chamber and light of wavelength 200nm is directed at it. The ball and the chamber are both initially at zero electrostatic potential. Electrons ejected from the ball causes the electrostatic potential to change.
    Describe the magnitude of the current ejected from the ball and the electrostatic potential of the ball, both as a function of time, assuming the radiation stays constant. Assume the current changes linearly with respect to the potential and that the capacitance of the ball is C.

    The work function of silver (4.7 eV) is also given.

    3. The attempt at a solution
    I understand physically what is happening in this problem. The radiation causes electrons to be ejected and causes charge build-up on the walls of the chamber and the ball which increases the electrostatic potential. Also, I realize that as the potential increases, it is more difficult for the charge to flow, and when the potential reaches the stopping voltage (I already calculated this to be 1.5 eV), there will be no current flow.
    I just can't work out the problem on paper using the linear relationship... help!
  2. jcsd
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