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Homework Help: De broglie

  1. Oct 31, 2005 #1
    how do you find the kinetic energy of an electron whose de Broglie wavelength is the same as that of a 100keV x-ray?
  2. jcsd
  3. Oct 31, 2005 #2
    Since the de Broglie wavelength is given by the momentum of the particle, I guess you would first determine the momentum p of the photon: p = E/c (I think), then find the kinetic energy of the electron via 0.5p^2/m, where m is the electron mass.
  4. Nov 1, 2005 #3
    it's not a photon, but can you still use that formula?
  5. Nov 1, 2005 #4
    Yes, you can use the de Broglie formula h/p to find the wavelength of an electron or a photon. The difference between the two comes in determining p. For an electron, p = mv. For a photon, p = E/c.

    So if your photon has energy E = 100 keV, convert this to Joules and use p = E/c to find the momentum of the photon.

    If the de Broglie wave of the electron has the same wavelength, it must have the same momentum p.
  6. Nov 1, 2005 #5
    ok, thanks!
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