In a dispersive system v-phase > v-sound
> v-group...This clip works best in QuickTime (available free from Apple for Mac and for Win 95/98/NT/ME/2000/XP)
In a wavepacket or pulse, the group velocity is less than c, the phase speed is greater than c; v-group*v-phase=c^2.
Last revised: 12 March 2003 - rsm