On Tue, 12 Feb 2008 07:08:19 -0600, "amdx" wrote:

Can someone explain how these two relate in a waveguide.
My limited understanding is, group velocity is slow near cutoff and
increases as frequency increases to almost c.
I don't know the difference between group velocity and phase velocity.
Thanks, Mike


---
If you threw a stone into a pond, the group velocity of the wave
generated would be how fast the ripples moved away from the point
where the stone hit the water, while the phase velocity would be how
long it took for a ripple peak to go from a peak to a trough and
then back to a peak.

Likening it to a pair of scissors closing while cutting through a
sheet of paper, the group velocity would be the speed of the ends of
the blades approaching each other, while the phase velocity would be
the speed of propagation of the cut as the blades sliced the paper
apart.

--
JF