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Homework Help: Velocity of Wave Packets

  1. Jan 17, 2005 #1
    Wave packets has a group velocity of


    and its phase velocity is


    Show that the group velocity and the phase velocity are related by:

    [tex]v_{group} = v_{phase} - \lambda\frac{dv_{phase}}{d\lambda}[/tex]

    Can someone please tell me where to start on this problem?
  2. jcsd
  3. Jan 17, 2005 #2


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    Homework Helper

    All u need to know besides the rules of differentiation is
    [tex] k=:\frac{2\pi}{\lambda} [/tex]


    PS.Compute the RHS of your equality and show it matches the LHS.
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