Michael Motyka writes:
> I'm a bit rusty but isn't it the other way around? Phase velocity may
> exceed 55mph( 25 in a school zone ) but group velocity ( information,
> energy ) is limited? I thought the envelope was what carried energy.
Group velocity is the speed at which the envelope moves. Phase velocity
is the speed at which the peaks move, and is constrained to be the speed
of light in the medium. Group velocity is the speed at which energy is
transported, but signalling cannot be done at greater than the phase
velocity.
If the phase velocity is not a function of wavelength, then the phase and
group velocities are equal. If the medium is not linear in this respect,
we get a phenomena known as "dispersion," which in most materials results
in the group velocity being lower than the phase velocity by a few
percent, and sometimes a phenomena known as "anomalous dispersion" in
which the phase velocity exceeds the group velocity.
> IPO's a bit out of fashion as of late?
Yes.
--
Eric Michael Cordian 0+
O:.T:.O:. Mathematical Munitions Division
"Do What Thou Wilt Shall Be The Whole Of The Law"
