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Homework Help: Photoelectric effect and current

  1. Jul 9, 2008 #1
    In a photoelectric effect experiment, which of the following changes by result in a current, if there was no current flowing previously?

    1. decreasing voltage in apparatus
    2. decreasing frequency of the incident light
    3. making the incident light brighter
    4. increasing wavelength of the incident light
    5. making the color of the incident light bluer

    So I've done some research and I came across the fact that "Larger radiation intensity or frequency would produce more current."

    source: http://en.wikipedia.org/wiki/Photoelectric_effect

    So I've narrowed down the answer choices to 3 and 5. but not sure which one is right. can someone help me? thanks.
  2. jcsd
  3. Jul 9, 2008 #2
    What you say about larger intensity/frequency is absolutely right. Take a look at the electromagnetic spectrum. If you're making the light bluer are you increasing the frequency or decreasing it?
  4. Jul 9, 2008 #3


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    There's actually a lot of difference between something changing from zero photoelectric current flow to some current flow and some current flow to larger current. Just think about why there may be zero current flow in the first place.
  5. Jul 9, 2008 #4
    I looked at the electromagnetic spectrum. By bluer does it mean a darker blue, if so the wavelenght decreases so frequency increases. But the other choice says making the light brighter does that mean increasing intensity or just making it go for let's say blue to yellow?
  6. Jul 9, 2008 #5
    I don't know the reason why, but I have learned of something called the stopping voltage?
  7. Jul 9, 2008 #6


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    It may be due to more than one factor, and I suspect that your original question may either be poorly worded or there is more than 1 answer.
  8. Jul 9, 2008 #7
    If there was NO current flowing at a certain frequency of light, it doesn't matter how intense the light beam is, no current will flow (because no electrons are excited).
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