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Photoelectric effect

  1. Jun 7, 2004 #1
    it state electron will be released from a metal surface if exposed to electromagnetic

    so i was thinking on a sunny day, a particular metal exposed to sun light one of the emf,, would the electron start to fly off the surface?

    if it does,? isnt this radiation? or it is un-notice-able?

  2. jcsd
  3. Jun 7, 2004 #2

    Chi Meson

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    "one of the emf..."" no sense.

    I'm guessing what you are asking, is does the photoelectric effect cause electrons to spray off of a metal if it is left out on a sunny day?

    Yes and no.

    THe photoelectric effect would indeed cause electrons to receive the energy required to "escape" the piece of metal, but once the electron leaves, then the metal will have a net positive charge, and the electron will of course be negatively charged. THe next electron would have to receive even more energy to escape the metal that is now already positively charged, the third electron even more, etc etc. So after a very short while there will no longer be any electrons emitted because there would be too much electrostatic attraction for an electron to overcome (I don't know how many electrons, thousands? millions?) and the effect would stop.

    It would be hard to detect this current, since even millions of electrons flowing per second is only one trillionth of an amp. One way to see evidence of this effect is to expose zinc that has been negatively charged to direct sunlight. Using an electroscope you can see the charge leaks off the zinc much faster than without sunlight. Evidently, a strong UV lamp can cause the zinc to show a positive charge after it loses lots of photoelectrons (you need a sesitive electroscope, I never got this to work)

    No matter what, you would not SEE any visual effect of radiation of any sort.
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