What is the Speed of Galaxies by Redshift?

[iamthemeg]

Homework Statement

I am trying to calculate, from their redshifts, the speed at which each of the following galaxies is moving away from us. Give your answers in both km/s and as a fraction of the speed of light.

The galaxies are:
Galaxy 1: Observed wavelength of hydrogen line is 659.2 {\rm nanometers}.
Galaxy 2: Observed wavelength of hydrogen line is 664.4 {\rm nanometers}.
Galaxy 3: Observed wavelength of hydrogen line is 683.1 {\rm nanometers}.

Additional Info:
Imagine that you have obtained spectra for several galaxies and have measured the observed wavelength of a hydrogen emission line that has a rest wavelength of 656.3 nanometers. The above galaxies are the results.

 

[iamthemeg]

oops, that should read,
"Galaxy 1: Observed wavelength of hydrogen line is 659.2 nanometers.
Galaxy 2: Observed wavelength of hydrogen line is 664.4 nanometers.
Galaxy 3: Observed wavelength of hydrogen line is 683.1 nanometers. "