Velocity of Phase Wave in Vacuum - Contradicting Relativity?

[kmajhi]

Velocity of phase wave in vacuum is grater than light velocty. This contradict the princles of relativity,so how this can be possible.

 

[kith]

You cannot transmit information with a wave of a single frequency. In order to transmit information, you need to turn the wave on and off somehow. This introduces additional frequencies and you get a wave packet. Your information then propagates with the group velocity of this wave packet and not with the phase velocities of its wave components.

For matter waves, the group velocity is equal to the particle velocity which can't exceed c.

 

[bhobba]

Velocity of phase wave in vacuum is grater than light velocty. This contradict the princles of relativity,so how this can be possible.

That's from De-Broglies hypothesis which was simply a historical way-station to the full theory developed by Dirac in late 1926 and those old ideas were consigned to the dustbin of history - forget about them except in a historical context.

That said phase velocity is unobservable so that it propagates FTL is of zero concern.

Thanks
Bill