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The Doppler effect (also Doppler shift) is the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave. [ 1 ] [ 2 ] [ 3 ] The Doppler effect is named after the physicist Christian Doppler , who described the phenomenon in 1842.
Figure 10. The relativistic Doppler shift formula is applicable to both sound and light. First-year physics textbooks almost invariably analyze Doppler shift for sound in terms of Newtonian kinematics, while analyzing Doppler shift for light and electromagnetic phenomena in terms of relativistic kinematics.
where c is the speed of light. In the classical Doppler effect, the frequency of the source is not modified, but the recessional motion causes the illusion of a lower frequency. A more complete treatment of the Doppler redshift requires considering relativistic effects associated with motion of sources close to the speed of light.
Derivation of the relativistic Doppler shift If an object emits a beam of light or radiation, the frequency, wavelength, and energy of that light or radiation will look different to a moving observer than to one at rest with respect to the emitter.
A galaxy's recessional velocity is typically determined by measuring its redshift, a shift in the frequency of light emitted by the galaxy. The discovery of Hubble's law is attributed to work published by Edwin Hubble in 1929, [ 2 ] [ 3 ] [ 4 ] but the notion of the universe expanding at a calculable rate was first derived from general ...
Doppler Effect: Change of wavelength and frequency caused by motion of the source. The formula for radar Doppler shift is the same as that for reflection of light by a moving mirror. [3] There is no need to invoke Albert Einstein's theory of special relativity, because all observations are made in the same frame of reference. [4]
In physics and general relativity, gravitational redshift (known as Einstein shift in older literature) [1] [2] is the phenomenon that electromagnetic waves or photons travelling out of a gravitational well lose energy. This loss of energy corresponds to a decrease in the wave frequency and increase in the wavelength, known more generally as a ...
In physics, the Ives–Stilwell experiment tested the contribution of relativistic time dilation to the Doppler shift of light. [1] [2] The result was in agreement with the formula for the transverse Doppler effect and was the first direct, quantitative confirmation of the time dilation factor. Since then many Ives–Stilwell type experiments ...