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The Doppler Effect

July 26th Fact-of-the-Day

Christian Doppler predicted in 1842 that the frequencies of received waves are dependent upon any motion of a wave source or wave observer relative to a wave propagating medium. His prediction was tested soon after by alternately placing a moving sound source and then a moving sound observer on one of the recently developed railroad trains. In 1905 Albert Einstein 'coined' the expression 'Doppler shift' in the original article he published on the special theory of relativity where he explained that light wavelengths shift according to the velocity of a light source relative to an observer. Erwin Schrdinger later obtained the same result from his photon hypothesis for light. Since then, Doppler shift often is sited as one of the important equivalences of the intuitively-different wave and particle descriptions of light. ©2005 Martek International All rights reserved.

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