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Topic: Doppler shift


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In the News (Thu 23 May 19)

  
  Doppler effect - Wikipedia, the free encyclopedia
The Doppler effect, named after Christian Andreas Doppler, is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves.
This line shape is called a Doppler profile and the width of the line is proportional to the square root of the temperature of the gas, allowing the Doppler-broadened line to be used to measure the temperature of the emitting gas.
The LDV and ADV emit a light or acoustic beam, and measure the doppler shift in wavelengths of reflections from particles moving with the flow.
en.wikipedia.org /wiki/Doppler_effect   (1311 words)

  
 AllRefer.com - Doppler effect (Physics) - Encyclopedia
Doppler effect, change in the wavelength (or frequency) of energy in the form of waves, e.g., sound or light, as a result of motion of either the source or the receiver of the waves; the effect is named for the Austrian scientist Christian Doppler, who demonstrated the effect for sound.
The Doppler effect in reflected radio waves is employed in radar to sense the velocity of the object under surveillance.
The Doppler effect is responsible for the red shifts of distant galaxies, and also of quasars, and thus provides the best evidence for the expansion of the universe, as described by Hubble's law.
reference.allrefer.com /encyclopedia/D/Dopplere.html   (483 words)

  
 DOPPLER DF INSTRUMENTS/PULSES
Doppler shift is a change, or "shift", of (recieved) signal frequency caused by relative motion between a signal source and a signal detector.
The amount of Doppler shift (expressed in Hertz) is proportional to the "rest" carrier frequency, and the relative velocity between the source and detector.
Maximum phase shift occurs for signals approaching from a direction parallel to the antenna baseline, and is limited by the separation distance between the two antennas, expressed in wavelengths.
www.silcom.com /~pelican2/PULSES.html   (1040 words)

  
 Blue shift - Wikipedia, the free encyclopedia
Blue shift is the opposite of redshift, the latter being much more noted due to its importance to modern astronomy.
Blue shift is the phenomenon that the frequency of an electromagnetic wave (such as light) emitted by a source moving towards the observer is shifted towards the blue side of the electromagnetic spectrum (that is, its wavelength is decreased).
The phenomenon of shifting wavelengths in frames of reference moving relatively to each other is commonly known as Doppler shift or Doppler effect.
en.wikipedia.org /wiki/Blue_shift   (264 words)

  
 Doppler shift
Thus the ‘Doppler shift’ occurs as a result of the effect of time gradients on the speed of a photon.
Actually, the fact that wavelength shifts are detected would appear to be a persuasive observational indication that the speed of light is variable, at least for higher energy radiation.
The reasoning seems to be that the wavelength shift for light from a moving source must be the same as that for sound.
home.earthlink.net /~chkingston/DopplerShift.htm   (1436 words)

  
 C-ship: The Doppler Shift
From Doppler's formula, we can expect the frequency of sound approaching the train to be shifted to 10% higher pitch, and sounds receding shifted to 10% lower pitch, roughly the difference between two adjacent white keys on a piano keyboard.
The reason we notice the Doppler shift of sound but not of light is simply the consequence of the tremendous difference in the speed of sound and the speed of light.
The Doppler shift predicted by classical physics is shown in red and the correct prediction of special relativity in green.
www.fourmilab.ch /cship/doppler.html   (756 words)

  
 The Doppler Effect and Sonic Booms
His Doppler Effect is the shift in frequency and wavelength of waves which results from a source moving with respect to the medium, a receiver moving with respect to the medium, or even a moving medium.
A red shift occurs when the source and observer are moving away from eachother, and a blue shift occurs when the source and observer are moving towards eachother.
Doppler Radar uses the doppler effect for electromagetic waves to predict the weather.
www.gmi.edu /~drussell/Demos/doppler/doppler.html   (1050 words)

  
 sciforums.com - The Doppler Shift Myth.
--> The Doppler shift is most simply defined as the apparent wavelength differences observecd from photons emitted from a source that is either moving toward he observer, wavelength compression, or wavlength extension when the source moves away from the direction of the emitted photons.
First understand Doppler shift as it applies to sound waves, since that is a familiar and obvious example.
Of course, you are absolutely right: the Doppler effect is a pure kinematics phenomenon and occurs due to observation of wave from the two reference frames moving in respect of each other.
www.sciforums.com /showthread.php?p=716603   (2153 words)

  
 RLTN3813 Unit 7
The Doppler shift or frequency shift is the difference between the sound source frequency and the perceived frequency at the sound receiver.
Note the frequency shift is influenced by the relative motion between the sound source and receiver and by the original (source) frequency.
The Doppler shift calculations are used by medical Doppler instruments to estimate vascular and cardiac blood flow velocities.
moon.ouhsc.edu /kboyce/rltn3813/3813u7.htm   (1808 words)

  
 A Closeup of Doppler Shift
Doppler shift is a phenomenon which is commonly observed by the lay person, yet still confuses many amateur satellite operators.
Doppler shift is proportional to the frequency of operation, so it becomes more significant on the higher bands.
Doppler shift is inherent in any mobile radio communications, but is only significant to amateurs at extremely high frequencies, or for satellite operation.
www.qsl.net /vk3jed/doppler.html   (1190 words)

  
 Emergency Ultrasound
The Doppler shift is the difference in sound frequency between the US beam transmitted into tissue and the echo produced by reflection from the moving red blood cells (RBCs).
The amount of frequency shift is proportional to the velocity of the moving RBCs.
Ft is the frequency of the transmitted Doppler beam and Fr is the frequency of the Doppler echo returned to the transducer.
www.med-ed.virginia.edu /courses/rad/edus/index4a.html   (439 words)

  
 Doppler Shift
Christian Johann Doppler (probably Döppler; 1803-1853) probably had such double stars in mind when he wrote in 1842 that perhaps the difference in colors were due to the motion of the stars, since the frequency of the light from an approaching star should be increased, and from a receding star decreased.
The optical Doppler effect was not observed until 1905, when J. Stark found that the light emitted by canal rays, which are fast ions from the cathode of a glow discharge, was Doppler-shifted by the expected amount.
The red shift of the light from distant galaxies is also famous, and is usually interpreted as due to a recessional velocity increasing linearly with distance, though the argument is in danger of being a circular one.
www.du.edu /~jcalvert/phys/doppler.htm   (2886 words)

  
 Doppler Shift Spectroscopy   (Site not responding. Last check: 2007-11-07)
Doppler shifted spectroscopy is used to determine beam specie fraction.
By observing and logging the Doppler Shift of emitted light and its intensity, the species mix in the beam can be determined.
The emitted light from the excited neutrals decaying to ground are blue shifted with respect to the fiber set in the direction counter the beam path.
fusion.gat.com /beams/diagnostics/species.html   (367 words)

  
 [No title]   (Site not responding. Last check: 2007-11-07)
DOPPLER Probably the best way to identify a signal source as a satellite, is Doppler shift.
Geostationary satellites have almost no doppler shift on their signals but they reveal what they are by staying in exactly the same place in your sky on the geostationary arc equator wards of your station, all day and night.
Indeed doppler shift can tell you lots more particularly if you are interested in propagation of radio waves, but that must wait for another satgen as it does not really concern the satellite spotter.
www.amsat.org /amsat/ftp/articles/satgen/sgen254.txt   (562 words)

  
 Part 6: Red Shift
Specifically, the galaxies' light spectra were shifted toward the red end of the spectrum.
Hubble and others realized that the most obvious explanation for the "red shift" was that the galaxies were receding from Earth and each other, and the farther the galaxy, the faster the recession.
This conclusion is based on a cosmological effect that is similar to the everyday "Doppler shift." Doppler shift is what makes a car sound lower-pitched as it moves away from you.
www.arachnoid.com /sky/redshift.html   (525 words)

  
 Howstuffworks "How Radar Works"
Doppler shift occurs when sound is generated by, or reflected off of, a moving object.
Doppler shift: The person behind the car hears a lower tone than the driver because the car is moving away.
The wake forms a V shape, and the angle of the V is controlled by the speed of the boat.
science.howstuffworks.com /radar1.htm   (875 words)

  
 The Doppler Effect   (Site not responding. Last check: 2007-11-07)
In this case it is not the pitch but the color (that is, the wavelength) that is shifted by the motion of the source.
The wavelength is shifted to larger values if the motion of the source is away from the observer and to smaller values if the motion is toward the observer.
The shift to larger wavelengths by motion away from the observer is called a red shift by astronomers and a shift to shorter wavelengths caused by motion toward the observer is called a blue shift.
csep10.phys.utk.edu /astr162/lect/light/doppler.html   (193 words)

  
 The CREIL Effect explaining Doppler Red Shift and Quasars. - Bad Astronomy and Universe Today Forum
It is equivalent to write that the spectrum of the light of stars is shifted towards the red, and that of the cold light towards blue (for this thermal radiation, this blueing is a reheating, an amplification).
The more the spectrum of a star is shifted towards the red, and the more distant the star is: this is the law of Hubble, explained from now on by effect CREIL and not by the Doppler effect which introduces an expansion of the Universe.
It is equivalent d?écrire that the spectrum of the light of stars is shifted towards the red, and that of the cold light towards blue (for this thermal radiation, this blueing is a reheating, an amplification).
www.bautforum.com /showthread.php?t=9585   (4201 words)

  
 Doppler Effect -- Theory
Doppler effect describes the frequency shift of the signal in relation to the relative motion of a source and an observer.
The wave generated by a source that moves away from an observer/receiver appears to him to be of lower frequency than the wave generated by a stationary source, or generated by a source moving toward the observer.
In case when the source is moving and the observer is still, the Doppler shift appears because the wavelength is changes.
physics.nad.ru /Physics/English/dopp_txt.htm   (408 words)

  
 Relativistic Doppler Shift   (Site not responding. Last check: 2007-11-07)
We learned before about the Doppler shift, that is the change in the wavelength of a spectral line due to the motion of its source.
Since galaxies are moving away from us, their doppler shifts are always positive, that is, the wavelengths of the spectral lines are redshifted.
Astronomers use the expression redshift, denoted usually by z, to indicate the magnitude of the doppler shift.
astrosun.tn.cornell.edu /academics/courses/astro201/doppler_rel.htm   (85 words)

  
 Physics 20 - Characteristics of Sound - The Doppler Effect   (Site not responding. Last check: 2007-11-07)
A similar effect (Doppler Shift for light) can also be used to determine the speed of a star relative to the earth.
The red shift of the star's spectrum indicates that the distance between an observed star and the earth may be increasing.
Note that, unlike the Doppler shift for sound, it does not matter whether the source or the observer is the one in motion.
www.sasked.gov.sk.ca /docs/physics/u5c32phy.html   (638 words)

  
 Doppler shift   (Site not responding. Last check: 2007-11-07)
In 1842 Doppler noticed that when a source of a wave moves along the line of sight of an observer, the wavelength changes.
There is no Doppler shift if the source is moving in the direction perpendicular to the observer.
The Doppler shift is observed both in sound waves and electromagnetic waves.
physics.csustan.edu /Ana/doppler.htm   (173 words)

  
 Doppler Principles (Police Traffic Radar Handbook)
The Doppler effect is a frequency shift that results from relative motion between a frequency source and a listener.
The Doppler shift is directly proportional to speed between source and listener, frequency of the source, and the speed the wave travels (speed of light for electromagnetic waves).
Reflections are frequency shifted (Doppler shift) if the target is moving; the faster the target is traveling, the more the frequency shifts.
copradar.com /preview/chapt2/ch2d1.html   (722 words)

  
 Doppler Shift
The spectrum from M31 reflects the fact that M31 is moving with respect to the Earth, and the light it emits is therefore Doppler shifted.
This is an example of what is called the Doppler shift, and it is an effect that is associated with any wave phenomena (such as sound waves).
You should also be able to easily convince yourself that the shift will yield an increase in the perceived frequency whenever the source and the observer are approaching one another, and a decrease in the perceived frequency whenever the source and the observer are moving away from each other.
imagine.gsfc.nasa.gov /YBA/M31-velocity/Doppler-shift-2.html   (1056 words)

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