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Homework Help: Group and phase velocity of a wave

  1. Dec 7, 2015 #1
    If i am given the de broglie wavelength
    Of any particle then its sure that i can find the velocity of tat particle if its mass is given.
    λ= h/mv
    But the velocity which i found is the group velocity or phase velocity?

    If it's not the group velocity
    How can i find it?
  2. jcsd
  3. Dec 7, 2015 #2

    Ken G

    User Avatar
    Gold Member

    If the particle has a definite momentum, it has a definite velocity, so the group velocity is the same as the phase velocity in that case. They are different if you have a "wave packet", which is a state of indeterminate momentum.
  4. Dec 7, 2015 #3
    If the particle electron is moving nearly at speed of light then also
    Is phase and grp velocities the same?
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