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: 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 .. :)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook