Calculating Frequency of Hydrogen Light in a Moving Galaxy

[_Mayday_]

Homework Statement

A galaxy is moving away from the Earth at a speed of 2.3\times 10^7 m/s^1. Hydrogen emits light of wavelength 410nm. The speed of light is 3.0\times 10^8 m/s^1 Calculate th frequency of hydrogen light emission that you would expect to measure on earth.

Homework Equations

I'm not really sure! I would have thought judging by what I have done previous to this.

V=f\lambda

\frac{\Delta f}{f} = \frac {v}{c}

The Attempt at a Solution

I really can't think of anything, I would have thought there were 2 steps to it. Possibly the first equation to find the frequency of Hygrogen? I'm really stuck

Help would be great

 

[psi^]

All you have to do is to compute the change in frequency due to Doppler's Effect, you have the speed of the source and the speed of the wave.
Check the general section on the wiki for more details on the formulas :)
http://en.wikipedia.org/wiki/Doppler_effect