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The "velocity" of a wave is a more subtle concept. In fact, there are several kinds of wave velocities, the
most common of which are group velocity and phase velocity. Group velocity is the speed of energy
and information propagation and, for an electromagnetic wave, must be less than the speed of light c. However,
the velocity at which the phase of the wave travels can be greater than the group velocity. The relationship
between the two is called the dispersion relationship.
For a general wave of wavelength and frequency , the group velocity is given by
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For a sinusoidal wave,
so
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and
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P-Wave, S-Wave, Speed of Sound, String, Velocity, Wave
© 1996-2007 Eric W. Weisstein
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