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Photoelectric effect threshold

  1. Oct 13, 2014 #1
    When a cm thick surface is illuminated with light of wavelength lambda,the stopping potential is V. When the same surface is illuminated by light of wavelength 2lambda , the stopping potential is V/3.The threshold wavelength for the surface is ?


    2. Relevant equations


    3. The attempt at a solution
     
  2. jcsd
  3. Oct 13, 2014 #2

    Matterwave

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    Did you try to do this problem yourself?
     
  4. Oct 14, 2014 #3
    Yes i tried but i am unable to solve it.
     
  5. Oct 14, 2014 #4

    NascentOxygen

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    Staff: Mentor

    Hi Nairabhi. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    What equations do you have that you'll use here?
     
    Last edited by a moderator: May 7, 2017
  6. Oct 14, 2014 #5
    See according to Einstein equation KE(Max)= Energy of photons - work function of surface, but since work function is not given i have assumed it
    to be 0. And energy of photons is equal to hc/lamda and this energy is equal to KE(Max) or the stopping potential so using these equations and i am trying to find a relation between them and find the threshold wavelength .However i don't understand what role does the thickness of surface plays which is 1cm ?
     
    Last edited by a moderator: May 7, 2017
  7. Oct 14, 2014 #6

    NascentOxygen

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    You should assume work function is non-zero, and is fixed at some value.

    That material thickness may simply mean "of suitable thickness" for our purposes.

    Does the textbook give the correct answer?
     
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