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Homework Help: Number of photons emitted from a laser

  1. Sep 15, 2010 #1
    1. The problem statement, all variables and given/known data
    A 35mW laser produces 526nm green light.
    What is the number of photons it emits each second?
    1.9×1017
    1.9×1018
    1.0×1017
    9.3×1016


    2. Relevant equations



    3. The attempt at a solution
    I've been playing with E=hf and lambda = h/p ----- no success!
    The text book im using doesn't have much on photons/photoelectric effect - nothing that helps me with this question at least. the "photon wavelength-momentum relation" is I think the most relevant to this question?? The text book doesn't actually say what p is so I assumed number of photons but thats wrong since it doesn't work.

    anyway need some help please.
     
  2. jcsd
  3. Sep 15, 2010 #2

    ehild

    User Avatar
    Homework Helper

    Calculate the energy of one photon. You need to get the frequency from the wavelength.

    ehild
     
  4. Sep 15, 2010 #3
    thanks ehild - solved the problem
     
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