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Homework Help: Find the de Broglie wavelength of an electron

  1. Sep 4, 2006 #1
    Find the de Broglie wavelength of an electron with KE:
    a]10eV
    b]1KeV
    c]1MeV
    d]100MeV

    Formulae:
    Relativistic
    [tex]\lambda = \frac{h}{\sqrt{{(E/c)}^2 - m_0^2c^4}}[/tex]

    Non-relativistic
    [tex]\lambda = \frac{h}{\sqrt{2mE}}[/tex]

    I am wondering for which case(s) should I apply the relativistic or the non-relativistic equation given that the BE of electron is 0.511MeV.
     
  2. jcsd
  3. Sep 4, 2006 #2
    The nonrelativistic approximation is generally good enough until the KE is about 5 or 10% of the rest energy.
     
  4. Sep 4, 2006 #3

    Andrew Mason

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    Science Advisor
    Homework Helper

    If the energy of the electron is much less than this, the electron is non-relativistic. Otherwise use the relativistic formula.

    AM
     
    Last edited: Sep 4, 2006
  5. Sep 5, 2006 #4
    Thanks inha and Andrew for the help!
     
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