Observing a change in the frequency or wavelength of a wave by an observer moving relative to the source of the waves is called as Doppler effect. Red shift happens when there is a shift of visible light in the red end or low frequencies of the spectrum. Here is the Doppler effect red shift velocity formula which allows you to determine the red shift velocity by multiplying the divided value of emitted wavelength and red shift wavelength reduced by 1 with speed.