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Homework Help: Photo electric effect

  1. Mar 28, 2010 #1
    1. The problem statement, all variables and given/known data
    In converting electrical energy into light energy, a sixty-watt incandescent light bulb operates at
    about 2.2% efficiency. Assuming that all of the light is green light (wavelength approximately
    5500 Å), determine the number of photons per second given off by the bulb and B:if you were to look directly at the bulb, the light
    from it would travel directly to your eye without reflecting from anything. If you stand 3.5
    meters away and look at the bulb for only 0.10 seconds, how many photons will enter your eye?
    (assume the pupil of your eye has a diameter of 2.1 mm)

    2. Relevant equations
    I don't really know what to use.
    I think E= hf

    3. The attempt at a solution
    First I converted angstroms to wavelength then I found frequency. From frequency and planks constant I found E but then I got nothing . DOn't even know how to touch B.
  2. jcsd
  3. Mar 28, 2010 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper

    For (A), you need to answer two questions first:

    1. How many Joules per second are produced in the form of visible light?

    2. How many Joules of energy are in one photon? (Use the answer you got from using E=hf)
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