1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    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!

Homework Help: Photoelectric effect

  1. Sep 28, 2009 #1
    1. Two seperate photocells are set up, using light sources with identical intensity and frequency, but with different metal cathodes, having different work functions. Which of these following are correct (more than 1 answer possible):
    A. The stopping Voltage will be identical
    B: The photoelectric current will be identical
    C: The smaller the work function, the larger stopping voltage
    D: The larger the work function, the larger maximum kinetic energy of photon electrons

    Well, the answers in the book are available, which are B and C. C is reasonable, since E(e) = hf - W (W = workfunction), the smaller W is, the larger E(e) and so, the larger stopping voltage neccessary. However, B is doubtful, since according to:
    E(e) = 0.5mv^2 = hf - W, the smaller the work function is, the higher the speed of electrons, so shouldn't the current produced be larger? (f constant here). (Since current I = q/t, the number of charges passing a particular passage over time, current depends on both speed of electrons and the actual numbers of electrons moving, doesn't it?.)
    My textbook (Heinemann Physics 12, 3rd ed., VCE Australia, some of you who come from Australia may know of it) does not mention anything about increasing frequency = increasing current, while http://en.wikipedia.org/wiki/Photoelectric_effect claims it to be true. Looking for your thoughts, thanks.

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted