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The Doppler Effect (sound)

 Doppler Effect Physics

The Physics of The Doppler effect was discovered by the Austrian physicist Christian Doppler in 1842. Everyone instinctively knows the doppler effect even if they do not realise they know it. It occurs anytime you hear a police car, ambulance (with their sirens on) or airplane approach you and then pass by.

Doppler Effect Physics

Doppler Effect Physics

In the case of a police car or ambulance, you can hear a change in the noise as the car/ambulance changes from approaching you, to passing you.

Applications of the Doppler Effect Physics

Doppler Radar

Medical Imaging

Flow Measurement

The Doppler Effect can also occur with light, this allows astronomers to estimate the speed at which a star/galaxy is moving away from us, this led to the formation of the big bang theory.  The reason for this is because no matter where in the sky astronomers looked, they found that almost all of the stars and galaxies were moving away from us, the only logical explanation for this would be that if you reversed time, then they would all be nearer to us, and if you reverse time enough, we would all end up at the same starting point.

All of these discoveries have been made because of one fairly straightforward law of physics, the doppler effect –