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Doppler effect (2)
With electromagnetic radiation the speed of the source will be much less than the speed of the waves. However in the case of sound it is quite possible that the speed of the observer or the source is significant compared with the speed of sound.

The frequency change equation used for electromagnetic radiation does not apply. The new frequency must be calculated from:
f = f/[1 v/c] and then the frequency change worked out from this.

The Doppler effect can be observed in the following examples:
(a) change in the pitch of a buzzer when it is whirled around your head
(b) the change in pitch of a train hooter or whistle as it passes through a station
(c) the shift of the frequency of the light from the two sides of the solar disc due to the Sun's rotation
(d) the variation in the frequency of the light from spectroscopic binaries
(e) in police radar speed traps
(f) Doppler broadening of spectral lines in high temperature plasmas
(g) measurement of the speed of the blood in a vein or artery
© Keith Gibbs 2009