Group and Phase Velocity

t

2.74

Δk

0.2805

Δω

-0.66

The group velocity

v

g

is the speed of the overall shape of a modulated wave (called the envelope). This is defined by

dω/dk

(chosen here to equal 1), where

ω

is the angular velocity and

k

is the wave number. The phase velocity

v

p

of a wave is the speed at which a given phase of a wave travels through space, equal to

ω/k

.