Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Threshold wavelength photoelectrons

  1. Aug 14, 2006 #1
    With what speed will the fastest photoelectrons be emitted from a surface wih threshold wavelength of 600nm when the surface is illuminated with light of wavelength of 400nm?
  2. jcsd
  3. Aug 14, 2006 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2018 Award

    Do you know the significance of the information given by the "threshold wavelength"? If I used a 600 nm light, what would be the energy of the photoelectrons that are emitted?

  4. Aug 14, 2006 #3
    the energy would be equal to the work function at 600nm because when the wavelength is at the threshold the energy is always equal to the work function.
  5. Aug 14, 2006 #4
    how does that help? i still don't understand.
  6. Aug 14, 2006 #5
    It tells you what the work function is.
  7. Aug 14, 2006 #6


    User Avatar
    Staff Emeritus
    Science Advisor

    Supplementing comments of ZapperZ and d_leet -

    One must determine the energy of the 600 nm photon, and that is sufficient to liberate (remove) an electron (photoelectron), hence the threshold.

    Calculate the energy of the 400 nm photon and compare to the energy of the 600 nm photon.

    Remember, the shorter the wavelength, the higher the frequency, which means more energy.
  8. Aug 16, 2006 #7
    E=hf. this is all you need
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook