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Maximum velocity of electrons?

  1. May 9, 2010 #1
    i've been trying to figure out this problem..

    The longest wavelength of light that causes electrons to be ejected from the surface of a copper plate is 243 nm. What is the maximum velocity of the electrons ejected when light of wavelength 200. nm shines on a copper plate?

    the answer is 6.22 × 105 m/s

    any ideas?
     
  2. jcsd
  3. May 10, 2010 #2
    Read about photoelectric effect.

    Ek=hf-φ

    Where φ is the work function, the lowest energy that must be supplied to tear off an electron, and hf>φ.
     
  4. May 10, 2010 #3

    alxm

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    Science Advisor

    Read the forum rules!
    This isn't the correct board for homework problems. And you should show some attempt to having solved the problem.
     
  5. May 10, 2010 #4
    thank you.. but how can i relate this to the wavelength concept?
    this is not a homework problem.. it is an old exam question..

    i would appreciate any additional information..
     
  6. May 10, 2010 #5
    [tex]f={c\over\lambda}[/tex]
     
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