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!

How to calculate the work function of a metal?

  1. Jul 14, 2013 #1
    HI im doing this equation : 14. When a certain metal is illuminated at 3.50x10^2nm the maximum kinetic energy of the ejected electrons is 1.20 eV. Calculate the work function of the metal.
    I did this:
    E=Ek+W
    W=E+Ek
    W=hc/Lambda -Ek
    =(6.63E-34J.s)(3.00E8m/s)/3.50E2m)-1.20eV
    =-1.2

    That answer is wrong the correct one is 2.35 eV. what did i do wrong, PLS help me ty and show me what I should of done so i Dont repeat this mistake again.
     
  2. jcsd
  3. Jul 14, 2013 #2
    Hello madayag1
    Look again at the figure you've used for the wavelength - you forgot the nm.
    Also, the first part of the calculation is in J, but you've subtracted a value in eV from it.
     
  4. Jul 14, 2013 #3
    Did you convert the units, Joule to eV?
     
  5. Jul 14, 2013 #4
    The result of 'W=hc/Lambda " is in joules is it not? You cannot subtract ev from joules wiothout a unit conversion.

    Also, you have ente3red your wavelength incorrectly.
     
  6. Jul 14, 2013 #5
    srry it should be W=( (6.63E-34J.s)(3.00E8m/s) / (3.50E2nm) ) - 1.9E-19J = -1.9E-19
    still the wrong answer tho.
     
  7. Jul 14, 2013 #6
    You've written the nm part for the wavelength, but did you include it in the calculation?
     
  8. Jul 14, 2013 #7
    Check your math. The answer is not negative. Also, what units are reque3sted?
     
  9. Jul 14, 2013 #8
    book doesn't say what units is requested
     
  10. Jul 14, 2013 #9
    I think work function is normally in ev. Check your math however.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted