ESS227
Prof. Jin-Yi Yu
Group
Velocity
•The group velocity of a wave is the velocity with which
the overall shape of the wave's
amplitudes (i.e. envelope) propagates through space.
•Two horizontally propagating waves of equal amplitude
but slightly different wavelengths
with wave numbers and frequencies differing by 2δk and 2δν, respectively. The total disturbance is thus:
high-frequency carrier wave
low-frequency amplitude
modulation
travels at the speed of δν/δk è
group velocity
