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Negative work function?

  1. Jul 29, 2007 #1
    Negative work function??


    I'm studying the photoelectric effect from the book of Zettili. It has an example that calculated the work function of lead knowing the maximum kinetic energy of the phtoelectrons (8.57 eV) for a given incident wavelength (280 nm). The result is W = - 4.14 eV.

    What does the negative sign mean?

  2. jcsd
  3. Jul 29, 2007 #2
    You send a 4.43 eV photon to the lead and you receive a 8.57 eV electron from it?
    It's the first time I heard of it.
    It could be quite useful to solve the energetic problems in the world!
    Apart from jokes, a possibility could be that occasionally, two photons are absorbed in sequence from a single electron. I knew this for energy levels in an atom but not for photoelectrons. Maybe two photons are absorbed by an atom putting it in an energy level with twice the energy of a single photon and then it releases it all to a single electron?
    Last edited: Jul 29, 2007
  4. Jul 29, 2007 #3


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    I'd like to see this example, because it makes no sense. The work function of Pb is around 4 eV based on standard references. If the term 'work function' has been redefined in that book to NOT be an attractive, bound potential, then the negative sign would be part of the value given. But this would be highly unusual, not to mention, confusing.

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