History of Group velocity

	Revision 4 . . October 28, 2001 7:14 am by DrBob [group velocity already covered in [[dispersion]]]
	Revision 3 . . (edit) October 27, 2001 9:21 pm by (logged).37.81.xxx [link fix]

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Difference (from prior major revision) (no other diffs)

Added: 12a13,17

Group velocity is mostly already covered under dispersion, this article should probably be a stub with a link to that one. BTW, "Recently, some bizarre cases have been found where the group velocity is faster than the speed of light" is incorrect, these cases were studied and understood by Sommerfield and Brillouin c.1930. What's new is that they used stimulated emission in the medium to amplify the light, that makes it much easier to see the effect. -- DrBob