In this example, the frequency of the second wave is slightly higher than the first. The two frequencies are close enough so that they form wave packets, or beats. The speed of the wave packets is called the group velocity. Note that the group velocity is a bit slower than the phase velocity of the individual waves; that is, the packets move slower than the single-frequency waves. This is typical for normal dispersion, where the speed of waves decreases as frequency increases.

Next: Group Velocity with Anomalous Dispersion
Previous: No Dispersion
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