Doppler ShiftFor a classical wave, imagine a pond of water on which a periodic disturbance is made. The disturbances generate a series of concentric outward moving pulses (waves). The wavelength is the distance between the pulses and the frequency is the rate at which the pulses pass by an observer. |
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Doppler ShiftFor a moving source, the point of periodic disturbance moves (to the right in the diagram). The disturbances still generate a series of outward moving circular pulses (waves), now however on the leading side the peaks are closer to together than on the trailing side. The detected wavelength then depends on the location of the observer. If the source approaches, the wavelength is shortened (blueshift). If the source recedes, the wavelength is lengthened (redshift). |
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