1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    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)
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Photo electric effect Date
Photo electric effect Oct 1, 2016
Photo electric effect problem May 21, 2015
Photo-electric effect, Compton Scattering Apr 28, 2012
Negative Work function in Photo electric effect Sep 22, 2011
Photo electric effect May 6, 2011