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posted by  DAAS on 9/5/2008 2:07:37 AM  |  status: Live  

calculate the kinetic energy of electrons??

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Given that the work function of chromium is 4.40 e , calculate the kinetic energy of electrons emitted from a chromium surface that is irradiated with ultraviolet radiation of wavelenght 200 nm.
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posted by Werner on 9/5/2008 6:36:22 AM  |  status: Live
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DAAS's comment:
"thanx a lot"
Response Details:
  Given that
  The work function of Cr, W = 4.40 eV
                                             = 4.4*1.6*10-19 J 
      The wave length of radiation λ = 200 nm
                                                     = 2.0 *10-7 m
    We know that
        (hc/λ) = W + K.E
   ∴ Kinetic energy K.E = (hc/λ)- W
                                     =  { (6.626*10-34 J s *3.0*108 m/s) / (2.0*10-7 m)}- 4.4*1.6*10-19 J
                                     =  9.939*10-19 J - (4.4*1.6*10-19 J)
                                     = 2.899*10-19 J
                                     = 1.8118 eV
   The kinetic energy of electrons emitted from a chromium surface = 1.8118 eV
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