This is the same formula as the group velocity of a wave.

Therefore, negative values of the group velocity will occur in these areas.

For this case, the phase and group velocities both are c.

In deep water the groups travel at a group velocity which is half of the phase speed.

In deep water this group velocity is proportional to the wave period.

The group velocity itself is usually a function of the wave's frequency.

This distortion is directly related to group velocity, as follows.

One derivation of the formula for group velocity is as follows.

Recently, it has become possible to create gases in which the group velocity is not only larger than the speed of light, but even negative.

Reversal of group velocity was explicitly announced in the related published paper.

Spin waves themselves have group velocities on the order of a few km per second.

The group velocity is depicted by the red lines (marked B) in the two figures above.

However, the wave's group velocity (associated with the energy flux) can be in any direction.

The group velocity is the wave speed of the modulation or envelope.

This means that phase- and group velocity of the waves are frequency dependent.

For a wave packet the group velocity is given by:

Slow light refers to a large reduction in the group velocity of light.

The group velocity also turns out to be the energy transport velocity.

Initially it was thought that the group velocity coincided with the speed at which information traveled.

The variation of group velocity creates the mode partition noise.

The opposite, group velocities exceeding c, has also been shown in experiment.

Group velocity is often considered to be the wave velocity at which information travels.

And the other cars were keeping pace or pulling ahead, so that the group velocity was deceptive.

A group velocity is basically the speed at which a wave group travels.

Most often, the group velocity is the velocity at which the energy moves through this medium.