The Doppler affect is a very widely known concept in Physics. When wave energy such as sound waves or radio waves travel from one object to another, the apparent wavelength might look changed provided that one or two of the objects are moving.
This is because the received frequency of the source might be totally different from the sent frequency, all because of the relative speeds adding up. In order to understand the Doppler affect, one must have sound expertise over relative speeds. This is because relative speeds are primarily responsible for the altered wavelengths of the waves at the receiving or sending end.
