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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.
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]
This shift, which the free-falling observer considers to be a kinematical Doppler shift, is thought of by the laboratory observer as a gravitational redshift. Such an effect was verified in the 1959 Pound–Rebka experiment. In a case such as this, where the gravitational field is uniform, the change in wavelength is given by
Doppler shift with source moving at an arbitrary angle with respect to the line between source and receiver. The analysis used in section Relativistic longitudinal Doppler effect can be extended in a straightforward fashion to calculate the Doppler shift for the case where the inertial motions of the source and receiver are at any specified angle.
Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planet's parent star. As of November 2022, about 19.5% of known extrasolar planets ...
A particular case is the thermal Doppler broadening due to the thermal motion of the particles. Then, the broadening depends only on the frequency of the spectral line, the mass of the emitting particles, and their temperature , and therefore can be used for inferring the temperature of an emitting (or absorbing) body being spectroscopically ...
Doppler spectrum. Deliberately no units given (but could be dBu and MHz for example). This is an issue only with a particular type of system; the pulse-Doppler radar, which uses the Doppler effect to resolve velocity from the apparent change in frequency caused by targets that have net radial velocities compared to the radar device. Examination ...
Radiation emitted by a moving source is subject to Doppler shift due to a finite line-of-sight velocity projection. If different parts of the emitting body have different velocities (along the line of sight), the resulting line will be broadened, with the line width proportional to the width of the velocity distribution.