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Homework Help: Modern Physics question

  1. Feb 7, 2010 #1
    Modern Physics question!!

    1. The problem statement, all variables and given/known data

    When radiation of wavelength 350nm is incident on a surface, the maximum kinetic energy of the photoelectrons is 1.2ev. What is the stopping potential for a wavelength of 230nm?

    2. Relevant equations
    [tex]\phi[/tex]=hc/[tex]\lambda[/tex]-eV0( V0= V 'nought')
    I am unsure as to what other equations can be used.


    3. The attempt at a solution
    My attempt was to calculate [tex]\phi[/tex] for the 350nm wavelength, and then do the same for the 230nm wavelength.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Feb 7, 2010 #2
    Re: Modern Physics question!!

    in this problem you can make use of two equations:
    (1) : Kmax = hc/lamda - workfunction (Kmax is the max. kinetic energy , lamda is the wavelength)

    (2) : Kmax = eVs (Vs is the stopping potential)


    your start is good .. when you get the work function for the 350 nm wavelength , use that workfunction again with equation (1) along with the 230 nm wavelength to get Kmax and then use equation (2) to get the stopping potential ..

    note : you just need to calculate the workfunction just once since that value is fixed for a certain material .. :)
     
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