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Homework Help: Photoelectric effect white light

  1. Oct 6, 2006 #1
    White light (ranging in wavelengths from 380 to 750 nm) is incident on a metal with work function Wo = 2.46 eV.
    (a) What is the maximum kinetic energy of the electrons emitted from the surface?

    KEmax = eV


    E = hf = hc/lamda.

    E = (6.626*10^-34)(3*10^8) / (750*10^-9) = 2.6504E-19

    I know to get KEmax i need to do 2.35- something = 0


    Thanks
     
  2. jcsd
  3. Oct 6, 2006 #2

    Astronuc

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    Note that energy of the photon is 'inversely proportional' to wavelength, and directly proportional to frequency.

    The KEmax(photoelectron) = Emax(photon) - Wo
     
  4. Oct 6, 2006 #3
    so i found emax which was 2.65E-19 right? so wat i would do is 2.65E-19 - 2.35???
     
  5. Oct 6, 2006 #4

    mrjeffy321

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    Your E_max value is the energy contained within the photon of light.
    For every photon absorbed (E_max worth of energy), some amount of that energy is spent removing the electron from the metal and the rest goes into the KE of the electron.

    KE_max_electron = E_max - W_o
    You are given a value for W_o in terms of electronvolts (a unit of energy) and you have previously calculated the E_max value, so you should be able to calculate from here the max KE value of the electron.

    1 eV = 1.602176462 E-19 Joules
     
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