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Phase velocity greater than propagation velocity

  1. Aug 29, 2008 #1


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    wavelength = 4 meters
    frequency = 30 cycles/sec
    period, T, = .033 sec/cycle
    wave propagation velocity = 120 m/s
    wave number ,k, = 2pi/wavelength = 1.57 radians/meter
    angular frequency, w, = 2pi/T = 188.5 radians/sec
    phase velocity = w/k = 120m/s
    In the above propagation velocity equals phase velocity
    Question: what values here would vary so that phase velocity is greater than propagation velocity ?
  2. jcsd
  3. Aug 30, 2008 #2


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  4. Aug 30, 2008 #3


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    I have a copy of the above but that is in reference to EM waves.
    Is it only in the case of electromagnetic waves where phase velocity can be greater than propagation velocity ?

    If not then I would like to see a numerical answer to my original question
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