Doppler Effect Uses

Introduction to Doppler effect uses:

The  whistle of a fast moving rain appears to increase in pitch as it approaches a stationary observer and it appears to decrease as the train moves away from the observer. This apparent change in frequency  was first observed and explained by Doppler in 1845.

The phenomenon of the apparent change in the frequency of sound due to the relative motion between the source of sound and the observer is called Doppler effect.Understanding Kinematics Formulas is always challenging for me but thanks to all science help websites to help me out.

The apparent frequency due to Doppler effect for different cases is deduced and this is applied in the various uses of Doppler effect.

Lets discuss the various uses of Doppler effect:

(i) To measure the speed of an automobile

An electromagnetic wave is emitted by a source attached to a police care. The wave is reflected by a moving vehicle, which acts as a moving source. There is a shift in the frequency of the reflected wave. From the frequency shift using beats, the speeding vehicles are trapped by the police.


Doppler effect uses - Tracing a satellite


The frequency of radio waves emitted by a satellite decreases as the satellite passes away from the Earth. The frequency received by the Earth station, combines with a constant frequency generated in the station gives the beat frequency . Using this, a satellite is tracked.

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Doppler effect uses - RADAR and SONAR


RADAR means Radio detection and ranging.

A RADAR sends high frequency radio waves towards an aeroplane. The reflected waves are detected by the receiver of the radar station. The difference in frequency is used to determine the speed of an aeroplane.

SONAR means Sound navigation and ranging

Sound waves generated from a ship fitted with SONAR are transmitted in water towards an approaching submarine . The frequency of the reflected waves is measured and hence the speed of the submarine is calculated.