# Waves- Group and Phase Velocities

1. Nov 11, 2008

### Fourier mn

Waves-- Group and Phase Velocities

1. The problem statement, all variables and given/known data
distance= 3*10^20 m
k=2$$\pi$$/$$\lambda$$.
$$\omega$$=(7.97*10^(-3)+ (KC)^2)^(1/2)
$$\omega$$= 1*10^9 Hz

2. Relevant equations
Phase Velocity= $$\omega$$/k
Group Velocity= d$$\omega$$/dk
t=d/v

3. The attempt at a solution

I wrote the phase velocity as-- (7.97*10^(-3) +(KC)^2)^(1/2)/k is that correct?
My group velocity is-- (the derivative of the above) -7.97*10^(-3)/(K^2$$\omega$$)
is it a correct statement?
Now, my biggest problem, I need to find the time it will take this wave to reach the Earth, any idea on how to do that?