Talk:Signal velocity

Can we have front velocity different to signal velocity? Say, slow (negative even) phase velocity but fast (positive) group velocity, so that most of the time the front slides backward but at regular intervals it jumps forward instantaneously: how would you average the front velocity? Cesiumfrog (talk) 02:39, 11 June 2008 (UTC)[reply]

Citation Needed

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However, in a few special cases (e.g., media designed to amplify the front-most parts of a pulse and then attenuate the back section of the pulse), group velocity can exceed the speed of light in vacuum, while the signal velocity will still be less than or equal to the speed of light in vacuum.

Crabpot8 (talk) 20:13, 23 December 2018 (UTC)[reply]