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Homework Help: Photoelectric effect

  1. Mar 20, 2010 #1
    1. The problem statement, all variables and given/known data
    What potential difference must be applied to stop the fastest photoelectrons by a nickel surface under the action of ultraviolet light of wavelength 220 nm? work function of nickel is 5.00eV.

    2. Relevant equations
    h[c]/[[tex]\lambda[/tex]] = [tex]\Phi[/tex] + eV

    3. The attempt at a solution
    h=6.6x10^-34 Js
    c=3.0x10^8 m/s
    [tex]\lambda[/tex]=200x10^-9 m

    [6.6x10^-34(3.0x10^8)]/[/200x10^-9] = 5.00 + 1.6x10^-19V
    9.9x10^-37 = 5.00 + 1.6x10^-19V
    9.9x10^37/5.00 = + 1.6x10^-19V
    1.98x10^37 / - 1.6x10^-19 =V
    v= 1.23x10^.18m/s

    not sure if this is right
    Last edited: Mar 20, 2010
  2. jcsd
  3. Mar 20, 2010 #2


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    Science Advisor
    Homework Helper
    Gold Member

    You need to convert the work function from eV to Joules before you plug it in.
  4. Mar 20, 2010 #3
    Also: really watch your units. As you have the equation solved... you're giving an answer in m/s... which doesn't make any sense. Carry your units along with the math... the problem is looking for a potential difference (and the solution should therefore be in volts).
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