# Doppler Effect

## 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