the apparent change in wavelength of sound or light emitted by an object in terms of an observer's position. An object nearing the observer have a shorter wavelength (blue) while an object going away will have a longer (red) wavelength. The Doppler impact could be used to approximate an object's speed and path.
by Cecil OlberdingReport definition
Definition for "Doppler Effect"
The obvious improvement in regularity or wavelength of…