Is the Group Velocity of Light Always Equal to c?

[Raparicio]

Dear Friends and Phorum,

I need to know how to calculate the group velocity of light. I've read that's exactly "c", but I don't know how to calculate it.

 

[quasar987]

How about this?

$$c=\lambda \nu = \frac{2\pi}{2\pi}\lambda \nu = \frac{\omega}{k}$$

So the dispersion relation is

$$\omega(k)=ck$$

There you go

$$v_g=\frac{d\omega}{dk} = c$$

 

[Raparicio]

Thanks You

Thanks quasar987