
Phase Velocity versus Group Velocity: Wave Dispersion - peter_d_sherman
https://www.youtube.com/watch?v=EIqKG5TiSYs
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peter_d_sherman
Observation:

Group velocity -- can potentially be much faster -- than any of its
constituent, individual phase velocity components, from other individual
waves...

Conversely, it should be possible to construct a relatively fast moving group
velocity wave -- by means of commingling two or more much slower individual
waves...

Also -- apparently by adjusting phase (all of the above occurs by phase
adjustment), you could also get a backwards-traveling group velocity wave,
even though the constituent individual phase velocity waves are forward
moving...

