phase/group velocity

[Physicsiscool]

Can anyone help me with this?

If w = square root of (gk) what is the phase and group velocity and show that the group velocity = v/2.

[somy]

Can you tell me what exactly the group velocity is???
I mean its definition. Thank a lot.
Somy :smile:

[dextercioby]

It's v_{g} =: \frac{d\omega(k)}{dk} ,where the \omega(k) is the dispersion relation.