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Quantum Physics: Calculating Photons/s

  1. Mar 18, 2009 #1
    1. The problem statement, all variables and given/known data

    I have another question,
    An incandescent light bulb consuming 75 W emits only 5% of this energy as visible light of wavelength 597 nm; the frequency of the emitted light is 5.02e+14 Hz. How many photons per second of this light does the bulb emit?

    2. Relevant equations

    E = hf

    3. The attempt at a solution

    E = (6.626068e-34)x(5.02513e14 Hz)= 3.3297e-28 J/photon

    75 W = 75 J/s

    (75 J/s)/(3.3297e-28 J/photon) = 2.252e29 photon/s

    but.... I'm wrong... I don't know why.
  2. jcsd
  3. Mar 18, 2009 #2
    oops.... 3.3297e-28 is actually 3.3297e-19....

    but that gives me 2.252e20 photons/s, which is still marked as incorrect, am I still missing something?
  4. Mar 18, 2009 #3
    oops, forgot the 5%, got it now.
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