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Homework Help: Different expressions for group velocity

  1. Mar 16, 2010 #1


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    1. The problem statement, all variables and given/known data

    Ok so we have different expressions for group velocity, g...

    The most obvious being g = dw/dk

    But then the text Im using says sinve w=vk we can write

    g = v+k dv/dk

    alongside other expressions, including k etc..

    My question is - what is v in the equation above? I thought there were only two characteristic velocities of a wave packet which is the superposition of many different waves - the group and phase velocities.. What is the physical meaning of v here..

  2. jcsd
  3. Mar 16, 2010 #2


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    Homework Helper
    Gold Member

    Compare the equation [itex]\omega=vk[/itex] to the definition of phase velocity and you will see:wink:
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