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De broglie vs classical wavelength

  1. Mar 10, 2007 #1
    since it is defined (from what i can tell) as h/p,

    is it interchangeable with the classical wavelength in equations involving waves in general? or is it a special separate case for matter?

    that is,

    for photons we have the following equation:
    E = hf
    E = hc/λ

    can the same equation be used to find the wavelength/energy of electrons?
  2. jcsd
  3. Mar 10, 2007 #2
    The de Broglie wavelength is now kinda viewed as the characteristic "size" of a quantum particle. It's not really a super-relevant physical quantity anymore, nor can you just put it into classical wave equations to get anything physical.
  4. Mar 10, 2007 #3

    Meir Achuz

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    For a photon E=pc, so the dB wavelength for a given energy is simple.
    For an electron p=\sqrt[{E^2/c^2-m^2}, so the dB wave length in terms of energy is more complicated,.
  5. Mar 10, 2007 #4
    we must include the rest mass of the electron?
  6. Mar 11, 2007 #5


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    Yes. And to get the frequency of the wave via E = hf, you must use the total energy (kinetic energy plus rest energy).
  7. Apr 16, 2007 #6
    According to de broglie relation lambda=h/mv ...which implies that velocity is inversely proportional to wavelength. But According to the reletion

    V=n lambda ... velocity is directly proportional to wavelength...... How That diffenence is Causesd ? Am i going wrong Somowhere ?
  8. Apr 16, 2007 #7


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    Note that the wave relationship only holds for massless particles.
  9. Apr 17, 2007 #8

    Meir Achuz

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    The V in V=\nu\lambda is the phase velocity of the traveling wave packet.
    This V also = E/p=h\nu/p, which is consistent.
    The phase velocity is >c, but the group velocity v_G=p/E is less than c.
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