How Does The Doppler Effect Work?


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Shalin Choksi Profile
Shalin Choksi answered
The Doppler Effect is the apparent change in the frequency of the sound, light or radio waves caused by the relative motion between the source of the waves and their receiver. For example, the pitch of a police car siren as the care speeds by depends on the whether the car is moving towards or away from you. As the car approaches, the sound waves ahead of it are bunched up. These short waves have a high frequency so the siren sounds high. Behind the car, the waves are stretched out.

These longer waves have a lower frequency so the siren sounds lower as the care drives past. In actual fact, the frequency of the siren does not change at all. Christian Doppler, who was an Austrian scientist, was the first to record the effect and hence the name was given.
Anonymous Profile
Anonymous answered
The apparent change in the pitch of sound due to the relative motion of source and observer is called Doppler Effect. There are some cases according to which Doppler Effect works.
Case1:  Moving Observer & Stationary Source
When observer moves towards the stationary source the apparent frequency of sound increases where as when it moves away from source, the apparent frequency of sound decreases.
Case2: Moving Source & Stationary Observer
When source moves towards the stationary observer the apparent frequency increases and when it move away then apparent frequency decreases.
Case3: Moving Source & Moving Observer
When both the source and observer move towards each other, the apparent frequency increases where as when they move away from each other the apparent frequency decreases.
Radar is one of the applications of Doppler Effect. - 11k 

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