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Homework Help: Photoelectric Effect - Query

  1. Feb 8, 2006 #1
    Im trying to get my head around a question in a book as i thought it would be good to give them ago as im struggling.

    The question is:

    Explain why a metal plate does not lose its charge when;

    a) the plate is + charged and illuminated with visible light.

    b) the plate is - charged and illuminated with UV light

    Also, when given wavelength and power of a wave, how do you work out the number of photons emitted per second?
    Last edited: Feb 8, 2006
  2. jcsd
  3. Feb 11, 2006 #2
    a)Even though the plate are being exposed for visible light, the light has not enough energy to free electrons from the metal.

    b)The plate has already a negative charge, and wont become positive if you expose it to UV light. The effect releases electrons, its not filling up whit them.
  4. Feb 21, 2006 #3
    I have a question about the photoelectric effect. Does it cause metal to decay? It involves emission of electrons from the metal and as far as I know there are no electrons being replaced: does the light cause the metal to break down after a long period of time?
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