Doppler effect

Dopplerdoppler shiftDoppler shiftsDoppler shiftingdoppler techniquesinverse Doppler effectblue-shiftedDoppler measurementsDoppler RadioDoppler-effect
The Doppler effect (or the Doppler shift) is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source.wikipedia
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Christian Doppler

Christian Andreas DopplerDoppler, ChristianDoppler, Christian Johann
It is named after the Austrian physicist Christian Doppler, who described the phenomenon in 1842.
He is celebrated for his principle — known as the Doppler effect — that the observed frequency of a wave depends on the relative speed of the source and the observer.

Über das farbige Licht der Doppelsterne und einiger anderer Gestirne des Himmels

Doppler first proposed this effect in 1842 in his treatise "Über das farbige Licht der Doppelsterne und einiger anderer Gestirne des Himmels" (On the coloured light of the binary stars and some other stars of the heavens).
Über das farbige Licht der Doppelsterne und einiger anderer Gestirne des Himmels is a treatise by Christian Doppler (1842) in which he postulated his principle that the observed frequency changes if either the source or the observer is moving, which later has been coined the Doppler effect.

Relativistic Doppler effect

transverse Doppler effectDoppler effectDoppler effect for electromagnetic waves
The Doppler effect for electromagnetic waves such as light is of great use in astronomy and results in either a so-called redshift or blueshift.
The relativistic Doppler effect is the change in frequency (and wavelength) of light, caused by the relative motion of the source and the observer (as in the classical Doppler effect), when taking into account effects described by the special theory of relativity.

Redshift

red shiftzred-shift
The Doppler effect for electromagnetic waves such as light is of great use in astronomy and results in either a so-called redshift or blueshift.
1) Objects move apart (or closer together) in space. This is an example of the Doppler effect.

Blueshift

blue shiftblue-shiftedblue-shift
The Doppler effect for electromagnetic waves such as light is of great use in astronomy and results in either a so-called redshift or blueshift.
Doppler blueshift is caused by movement of a source towards the observer.

Doppler spectroscopy

radial velocity methodradial velocityradial velocity measurements
This may be used to detect if an apparently single star is, in reality, a close binary, to measure the rotational speed of stars and galaxies, or to detect exoplanets.
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.

Hubble's law

Hubble constantcosmological redshiftHubble parameter
Rather, redshifting due to the expansion of space is known as cosmological redshift, which can be derived purely from the Robertson-Walker metric under the formalism of General Relativity.
2) This Doppler shift-measured velocity of various galaxies receding from the Earth is approximately proportional to their distance from the Earth for galaxies up to a few hundred megaparsecs away.

Hippolyte Fizeau

FizeauA. H. L. FizeauArmand Hippolyte L. Fizeau
Hippolyte Fizeau discovered independently the same phenomenon on electromagnetic waves in 1848 (in France, the effect is sometimes called "effet Doppler-Fizeau" but that name was not adopted by the rest of the world as Fizeau's discovery was six years after Doppler's proposal).
Fizeau was involved in the discovery of the Doppler effect, which is known in French as the Doppler–Fizeau effect.

Radial velocity

radial velocitiesradial-velocitydoppler velocity tests
It has been used to measure the speed at which stars and galaxies are approaching or receding from us; that is, their radial velocities.
Light from an object with a substantial relative radial velocity at emission will be subject to the Doppler effect, so the frequency of the light decreases for objects that were receding (redshift) and increases for objects that were approaching (blueshift).

Binary star

spectroscopic binaryeclipsing binarybinary
Doppler first proposed this effect in 1842 in his treatise "Über das farbige Licht der Doppelsterne und einiger anderer Gestirne des Himmels" (On the coloured light of the binary stars and some other stars of the heavens). This may be used to detect if an apparently single star is, in reality, a close binary, to measure the rotational speed of stars and galaxies, or to detect exoplanets.
Sometimes, the only evidence of a binary star comes from the Doppler effect on its emitted light.

C. H. D. Buys Ballot

Christophorus Buys BallotBallotBuys Ballot
The hypothesis was tested for sound waves by Buys Ballot in 1845.
Buys Ballot tested the Doppler effect for sound waves in 1845 by using a group of musicians playing a calibrated note on a train in the Utrecht-Amsterdam line.

Galaxy

galaxiesgalacticgalactic nuclei
It has been used to measure the speed at which stars and galaxies are approaching or receding from us; that is, their radial velocities.
Slipher discovered that the spiral nebulae have high Doppler shifts, indicating that they are moving at a rate exceeding the velocity of the stars he had measured.

Redshift-space distortions

Finger of Godredshift evolution
Having said this, it also happens that there are detectable Doppler effects on cosmological scales, which, if incorrectly interpreted as cosmological in origin, lead to the observation of redshift-space distortions.
The effect is due to the peculiar velocities of the galaxies causing a Doppler shift in addition to the redshift caused by the cosmological expansion.

John Scott Russell

solitary waveJohn RussellRussell
In Britain, John Scott Russell made an experimental study of the Doppler effect (1848).
of the Doppler effect which he published in 1848.

Laser Doppler velocimetry

laser Doppler velocimeterLaser Doppler Flowmetrylaser-doppler flowmetry
Instruments such as the laser Doppler velocimeter (LDV), and acoustic Doppler velocimeter (ADV) have been developed to measure velocities in a fluid flow.
Laser Doppler velocimetry (LDV), also known as laser Doppler anemometry (LDA), is the technique of using the Doppler shift in a laser beam to measure the velocity in transparent or semi-transparent fluid flows, or the linear or vibratory motion of opaque, reflecting, surfaces.

Sound

audiosound wavesound waves
For waves that propagate in a medium, such as sound waves, the velocity of the observer and of the source are relative to the medium in which the waves are transmitted.
Doppler effect

Cardiac output

cardiac inputoutputoutput of the heart
Velocity measurements allow assessment of cardiac valve areas and function, abnormal communications between the left and right side of the heart, leaking of blood through the valves (valvular regurgitation), and calculation of the cardiac output.
This method uses ultrasound and the Doppler effect to measure cardiac output.

Radar

radar stationradarsradar system
The Doppler effect is used in some types of radar, to measure the velocity of detected objects.
If the object is moving either toward or away from the transmitter, there is a slight equivalent change in the frequency of the radio waves, caused by the Doppler effect.

Laser Doppler vibrometer

laser vibrometervibrometerlaser Doppler vibrometry
A laser Doppler vibrometer (LDV) is a non-contact instrument for measuring vibration.
The laser beam from the LDV is directed at the surface of interest, and the vibration amplitude and frequency are extracted from the Doppler shift of the reflected laser beam frequency due to the motion of the surface.

Proximity fuze

proximity fuseproximityproximity fuses
Moreover, the proximity fuze, developed during World War II, relies upon Doppler radar to detonate explosives at the correct time, height, distance, etc.
Given their previous work on radio and radiosondes at NBS, Diamond and Hinman developed the first all solid-state radio doppler proximity fuze, which employed the Doppler effect of reflected radio waves using a diode detector arrangement that they devised.

Spectral line

emission lineabsorption lineabsorption lines
They exhibit absorption lines at well defined frequencies that are correlated with the energies required to excite electrons in various elements from one level to another.
Each photon emitted will be "red"- or "blue"-shifted by the Doppler effect depending on the velocity of the atom relative to the observer.

Relative velocity

relative motionrelative speedrelative velocities
Because the doppler shift affects the wave incident upon the target as well as the wave reflected back to the radar, the change in frequency observed by a radar due to a target moving at relative velocity \Delta v is twice that from the same target emitting a wave:
Doppler effect

Medical ultrasound

ultrasoundultrasonographysonogram
Velocity measurements of blood flow are also used in other fields of medical ultrasonography, such as obstetric ultrasonography and neurology.
Doppler ultrasonography is used to study blood flow and muscle motion.

Photoacoustic Doppler effect

Doppler
Photoacoustic Doppler effect
The photoacoustic Doppler effect, as its name implies, is one specific kind of Doppler effect, which occurs when an intensely modulated light wave induces a photoacoustic wave on moving particles with a specific frequency.

Hammond organ

organHammondHammond B-3 organ
The Leslie speaker, most commonly associated with and predominantly used with the famous Hammond organ, takes advantage of the Doppler effect by using an electric motor to rotate an acoustic horn around a loudspeaker, sending its sound in a circle.
This creates a characteristic sound because of the constantly changing pitch shifts that result from the Doppler effect created by the moving sound sources.