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Photoelectric effect units

  1. May 11, 2016 #1
    1. The problem statement, all variables and given/known data
    In a photoelectric experiment, a stopping potential of 2.70 eV is measured when ultraviolet light of wavelength 380 nm is incident on the metal. If blue light of wavelength 440 nm is used, what is the new stopping potential in eV?

    2. Relevant equations


    3. The attempt at a solution
    I think i understand how to do this problem (qV = hc/λ - work function) but am very confused as they have given and ask for the stopping potential in eV. I thought that eV was a unit of energy and that stopping potential (as it is a voltage) is given by the units V. How can the units of a potential be eV?
     
  2. jcsd
  3. May 11, 2016 #2

    phyzguy

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    You're right. The stopping potential should really be measured in V, not eV. But since it is electrons you are stopping, people sometimes get sloppy and refer to electron energy (in eV) rather than the potential (in V).
     
  4. May 11, 2016 #3
    So i should give the answer for the energy and not the potential?
     
  5. May 11, 2016 #4

    phyzguy

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    The numerical results should be the same. I would five the answer in V, and explain that the question is really incorrect, since potentials are measured in V.
     
  6. May 11, 2016 #5
    ok thank you very much!
     
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