Light

        Since light can be described as a wave, the Doppler Effect causes a shift in this case as well.  The Doppler Effect will cause a change in the color of the light; a shift toward the color red (a red shift) when the source is moving away from the observer or a shift toward the color blue (a blue shift) when the source is moving toward the observer.  The field of astronomy has benefited greatly from this discovery.  Astronomers are able to tell relative speeds of distant stars and galaxies either toward or away from our sun.

Picture retrieved from http://escience.anu.edu.au, 2004

Picture retrieved from csep10.phys.utk.edu