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The group velocity of a wave is

  • A.always equal to the phase velocity in every medium
  • B.the velocity of a point of constant phase
  • C.always greater than the phase velocity
  • D.the velocity at which energy and information travel

Answer: D

In a dispersive medium the phase velocity depends on frequency and a modulated signal travels at the group velocity instead, which is the derivative of angular frequency with respect to the wave number. In a non-dispersive medium the two coincide.

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