Definition

The apparent change ((increase / decrease) in the frequency (pitch) of sound (wave) due to relative motion between SOURCE and LISTENER along with the line of sight is called Doppler’s Effect.

Applications Of Doppler’s Effect :-

·         Principle of Doppler’s effect is used in RADAR to determine the position, distance and velocity of fast moving objects in SKY relative to the ground. Electromagnetic waves used in RADAR do not require a medium for propagation.

·         Also used in SONAR to determine the position, distance and velocity of submarines relative to the Ocean.

·         Used in ASTROPHYSICS to locate position, distance and velocity of Stars. The light received from the stars are found to have Doppler’s shift to frequency towards red end of the spectrum. This indicates stars are moving away from us.

·         Check speed of Automobiles: – A traffic officer can calculate the speed of an approaching or receding automobile by noting a change in the pitch of its horn. If the speed crosses safe limit, the driver can be booked for rash driving.