Experiment that gave the principle of Radar
In the year 1845,Christian Doppler an Austrian scientist, carried out a unique experiment. With the help of a friend he arranged for two freight trains, each carrying a set of musicians. One train remained stationary on the railway platform while the other passed the station with great speed. To Doppler and many other people standing on the platform one thing was obvious. The frequency of the music played by the two groups did not match, even though the musicians were playing a musical note of same pitch. You may wonder-why? The answer is- ‘Doppler Effect’. In 1842, Doppler had theorized that there is apparent change in the frequency of a sound if the source of the sound is moving in relation to the observer. Thus a sound wave will appear to have a higher frequency if the source is moving towards the observer and a lower frequency if the source is moving away from the observer. Earlier no one accepted this theory. But after the Train Experiment Doppler was proved to be right. Nowadays the ‘Doppler effect’ is widely used in measuring the speed of cars, ships and planes.
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