# Relation between phase velocity and group velocity

I know the physical meaning of phase as well as the group velocity.

I want to know the mathematical relationship between the phase velocity and group velocity.

Thanks a lot.

If you know the definitions, you can easily find a relationship.

If you know the definitions, you can easily find a relationship.

It looks as if the group velocity is the derivative of phase velocity but I don't think I am correct.

What's the exact relationship?

Thanks a lot.

It looks as if the group velocity is the derivative of phase velocity but I don't think I am correct.
The group velocity can be related to the derivative of phase velocity (in respect to k or λ
). It is not just equal to the derivative, it won't even make sens dimensionally. What relationship did you find?

The group velocity can be related to the derivative of phase velocity (in respect to k or λ
). It is not just equal to the derivative, it won't even make sens dimensionally. What relationship did you find?

Could not find anything.

morrobay
Gold Member
Could not find anything.
I did not mean to look it up but to find it by direct calculation.