“Doppler effect”的概念、定义、翻译、参考文献-科学参考

Doppler effect

Physics

The apparent change in the observed frequency of a wave as a result of relative motion between the source and the observer. For example, the sound made by a low-flying aircraft as it approaches appears to fall in pitch as it passes and flies away. In fact, the frequency of the aircraft engine remains constant but as it is approaching more sound waves per second impinge on the ear and as it recedes fewer sound waves per second impinge on the ear. The apparent frequency, F, is given by
$F = f (c - u_{o}) / (c - u_{s}),$

where f is the true frequency, c is the speed of sound, and u_o and u_s are the speeds of the observer and the source, respectively.

Although the example of sound is most commonly experienced, the effect was suggested by Christian Johann Doppler (1803–53), an Austrian physicist, as an attempt to explain the coloration of stars. In fact the Doppler effect cannot be observed visually in relation to the stars, although the effect does occur with electromagnetic radiation and the redshift of light from receding stars can be observed spectroscopically. The Doppler effect is also used in radar to distinguish between stationary and moving targets and to provide information regarding the speed of moving targets by measuring the frequency shift between the emitted and reflected radiation.

For electromagnetic radiation, the speed of light, c, features in the calculation and as there is no fixed medium to provide a frame of reference, relativity has to be taken into account, so that
$F = f \sqrt [(1 - v / c) / (1 + v / c)],$

where v is the speed at which source and observer are moving apart. If v²/c² is small compared to 1, i.e. if the speed of separation is small compared to the speed of light, this equation simplifies to
$F = f (1 - v / c) .$

Astronomy

See Doppler Shift.

Space Exploration

A change in the observed frequency (or wavelength) of waves due to relative motion between the wave source and the observer. The Doppler effect is responsible for the perceived change in pitch of a siren as it approaches and then recedes, and for the redshift of light from distant galaxies. It is named after the Austrian physicist Christian Doppler.
http://archive.ncsa.illinois.edu/Cyberia/Bima/doppler.html Discussion of the Doppler effect, including an explanation of how astronomers use it to calculate the speed with which celestial bodies are moving in relation to one another.

Electronics and Electrical Engineering

The change in the apparent frequency of a source of electromagnetic radiation (or sound) when there is relative motion between the source and the observer. The observed frequency $f'$ is given by
$f' = \frac{f (c - v_{o})}{(c - v_{s})},$
where c is the speed of light or sound, v_o is the velocity of the observer, and v_s is the velocity of the source.
The effect is utilized in Doppler navigation, which is a navigation system (in a moving object) that operates by ground reflection. Doppler radar employs the Doppler effect to distinguish between fixed and moving targets: the measurement of the change in the frequency of the reflected wave is used to determine the velocity and direction of the moving target.
http://www.einstein-online.info/spotlights/doppler Animations explaining the Doppler effect, from the Max Planck Institute
https://scratch.mit.edu/projects/12532039/ An interactive program showing the Doppler effect

单词	Doppler effect
释义	Doppler effect Physics The apparent change in the observed frequency of a wave as a result of relative motion between the source and the observer. For example, the sound made by a low-flying aircraft as it approaches appears to fall in pitch as it passes and flies away. In fact, the frequency of the aircraft engine remains constant but as it is approaching more sound waves per second impinge on the ear and as it recedes fewer sound waves per second impinge on the ear. The apparent frequency, F, is given by $F = f (c - u_{o}) / (c - u_{s}),$ where f is the true frequency, c is the speed of sound, and u_o and u_s are the speeds of the observer and the source, respectively. Although the example of sound is most commonly experienced, the effect was suggested by Christian Johann Doppler (1803–53), an Austrian physicist, as an attempt to explain the coloration of stars. In fact the Doppler effect cannot be observed visually in relation to the stars, although the effect does occur with electromagnetic radiation and the redshift of light from receding stars can be observed spectroscopically. The Doppler effect is also used in radar to distinguish between stationary and moving targets and to provide information regarding the speed of moving targets by measuring the frequency shift between the emitted and reflected radiation. For electromagnetic radiation, the speed of light, c, features in the calculation and as there is no fixed medium to provide a frame of reference, relativity has to be taken into account, so that $F = f \sqrt [(1 - v / c) / (1 + v / c)],$ where v is the speed at which source and observer are moving apart. If v²/c² is small compared to 1, i.e. if the speed of separation is small compared to the speed of light, this equation simplifies to $F = f (1 - v / c) .$ Astronomy See Doppler Shift. Space Exploration A change in the observed frequency (or wavelength) of waves due to relative motion between the wave source and the observer. The Doppler effect is responsible for the perceived change in pitch of a siren as it approaches and then recedes, and for the redshift of light from distant galaxies. It is named after the Austrian physicist Christian Doppler. http://archive.ncsa.illinois.edu/Cyberia/Bima/doppler.html Discussion of the Doppler effect, including an explanation of how astronomers use it to calculate the speed with which celestial bodies are moving in relation to one another. Electronics and Electrical Engineering The change in the apparent frequency of a source of electromagnetic radiation (or sound) when there is relative motion between the source and the observer. The observed frequency $f'$ is given by $f' = \frac{f (c - v_{o})}{(c - v_{s})},$ where c is the speed of light or sound, v_o is the velocity of the observer, and v_s is the velocity of the source. The effect is utilized in Doppler navigation, which is a navigation system (in a moving object) that operates by ground reflection. Doppler radar employs the Doppler effect to distinguish between fixed and moving targets: the measurement of the change in the frequency of the reflected wave is used to determine the velocity and direction of the moving target. http://www.einstein-online.info/spotlights/doppler Animations explaining the Doppler effect, from the Max Planck Institute https://scratch.mit.edu/projects/12532039/ An interactive program showing the Doppler effect
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