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Questions tagged [doppler-effect]

The Doppler effect refers to change in the observed frequency of a wave if the observer and source are in relative motion.

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Confusion about signs of the velocities in Doppler formula

Wikipedia gives the Doppler formula as: $ f = \left( \frac{c \pm v_r}{c \pm v_s} \right) f_0 $ c is the propagation speed of waves in the medium. $v_r$ is the speed of the receiver relative to the ...
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Doppler effect for multiple sources [closed]

Given the figure below, how can I determine the speed from the two sources given that they both produce a frequency of 1000 Hz, and the speed of sound can be assumed to 340 m/s. The sources are both ...
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Doppler shift from a moving reflector and source if only the relative velocity is known?

Suppose there is a device which is producing and listening to sound (sonar), a reflector is moving with respect to device and the velocity of reflector and device with respect to the air is not known, ...
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Doppler Effect and the concept of relative velocity in GR

While reading Sean Carroll's book on General Relativity, I understood that the concept of velocity is ill-defined over large distances in arbitrarily curved manifolds, like the one used to describe ...
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${}$Doppler shift

If observer is moving and source is at rest then i can treat the scenario with approach in which observer is at rest and source is moving since this is what will be happening according to the observer ...
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How does doppler cooling work?

I have trouble understanding how doppler cooling works. I understand that an atom moving towards laser sees the laser light blue-shifted and if the laser frequency is slightly below the atom's ...
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Oscillating body and Doppler effect

Say we have a body attached to a spring, oscillating with some frequency $\nu$. This is one of the simplest problems studied in elementary Physics, and yet I've noticed we always study it positioning ...
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Relativistic Doppler shift moving source in a circle

I am looking to understand the value for the relativistic doppler shift in the following scenario. We have a source moving in a circular pattern around a center. Now, if the observer would be in the ...
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$I_{\nu}/\nu^{3}$ which is Lorentz invariant is also invariant for cosmological redshift?

$I_{\nu}/\nu^{3}$ is Lorentz invariant, therefore an observed intensity is boosted by $\delta^{3}$, where $\delta$ is the Doppler factor. If the cosmological redshift is same physical process with ...
Chanwoo Song's user avatar
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Moving observer detects incoming photon: Is this the full derivation of the relativistic Doppler effect?

I have a very trivial question that I can't quite work out. Imagine an observer moving in Minkowski spacetime. In Cartesian coordinates $(ct,x,y,z)$, their 4-velocity is $$u^\mu = (u^t ,u^i )$$ where $...
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How is wavelength defined when it's changing continuously?

Take an observer, who is receiving an electromagnetic wave signal, which is constantly changing. It can be for example from a source of light falling into a black hole, so the observed wavelength is ...
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Is the Doppler effect for light symmetric?

This is a trick question but it leads up to the real question. Let me explain. The Doppler effect for sound is not symmetric. For a given relative velocity between source and receiver, the measured ...
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Was "flow of time" equally fast during the life of universe? Is Doppler Effect the only interpretation of "shift to red"? [duplicate]

I'm an IT developer and recently I created a project where I tried to send signals between two threads in a slowing down environment. I simulated two points with their own clocks and tried to send a ...
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Doppler shift of a single photon

I'm curious to understand how the Doppler shift phenomenon occurs and is mathematically expressed for a single photon emitted by a stationary single photon emitter, such as a quantum dot, and observed ...
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How to distinguish a doppler-shifted photon from a non-doppler-shifted photon of the same frequency?

Can one physically distinguish a photon of frequency $\omega$, generated by a stationary laser, from a photon generated by a mechanically moving laser (a different laser from the first one) which, due ...
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Doppler shift phenomenon for non-inertia frames

The Doppler shift phenomenon is well understood when the source and observer are in relative constant motion. However, I'm curious to know how the Doppler shift phenomenon is modified when they (i.e., ...
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Acceleration in flat space-time and gravitational redshift

Consider two observers in flat space-time, of which one, called Terrence, is stationary, while the other, called Stella, moves in an accelerated way. I am particularly interested in the case where ...
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Photoelectric Effect combined with Doppler Redshift

Suppose we were standing in the vacuum with a photoelectric effect experiment. If we had a source of EM radiation emitting photons with a high enough frequency, we would begin to observe said effect ...
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How does relativistic Doppler effect conserve energy?

Say I have a laser traveling at the stationary observer at relativistic speed, so the laser wavelength gets blueshifted. To conserve total energy emitted, according to the observer, the laser emits ...
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Anti-symmetry in Doppler Effect

I know the formula $\nu = \nu_{0}\frac{v + v_{o}}{v - v_{s}}$ for the Doppler Effect and saw that it gives different results in the cases where: 1- The source is stationary and the observer moves ...
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Doppler broadening upon reflection from liquid interface

I just came across the question "Why are the surfaces of most liquid so reflective?", in which the author asks how the surface of a liquid gives rise to a mirror image, even though it ...
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Relativistic Doppler Effect in a Medium

I am trying to find out how our relativistic Doppler effect formula would change taking into account mediums (not just vacuums), since the speed of light can drastically change depending on where the ...
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Gravitational redshift and doppler effect in Schwarzschild metric

I am trying to calculate the change in frequency of a photon emitted by beacon that has a circular orbit with $r=r_1$. In $r_2 >r_1$ there is a static observer that observes the photon when he, the ...
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Relativistic Doppler Shift vs Classical Doppler Shift Contradiction

In classical/Newtonian mechanics, the doppler shift (for light) can be expressed as: $$ \frac{f_r-f_s}{f_s}=\frac{1+\beta}{1-\beta}-1 $$ In relativity the doppler shift can be expressed as: $$ \frac{...
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Does the relativistic doppler effect breaks symmetries in the Twin Paradox?

It is often said that there is no experiment we can make that can determine if we are or aren't moving... this is one of the key aspects of the the Twin Paradox, but, if we accept the constant speed ...
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Is there a Doppler effect on the surface of an expanding balloon?

Imagine a stationary transmitter which vibrates the surface of the balloon and a stationary receiver half way around the balloon that can pick up these waves. Let the balloon expand. Will the ...
John Hobson's user avatar
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Optical path length for sound

The definition of optical path length is the distance that light could have travelled in the same time, in vacuum. So, can we define something analogous for sound waves, like an "acoustical path ...
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Does the Doppler effect change frequency?

Would a high-pitched unhearable frequency be heard whilst the doppler effect is in play? For example, when a car uses its horn whilst travelling by, the pitch shifts as it passes - which is the ...
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Maths behind red/blue-shifting [closed]

I watched this video of silly science facts, on of which stated "you can avoid red lights by travelling at around 114,000,000mph (51,000,000m/s) because the red light would be blue shited enough ...
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Analytical Solution of Sound Wave Propagation in Moving Medium (1D Problem)

I am trying to use frequency-wavenumber analysis to estimate sound wave propagation in a moving medium (fluid). I need to test the technique on analytical data. I wonder if there is an analytical ...
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Doppler shift in De Broglie's wavelength

If I were to take a particle, moving at a non relativistic velocity, it will have a wavelength (according to De Broglie). However, If I were to change the referance frame of the motion, I know that ...
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Doppler effect with a moving observer [duplicate]

I have seen the doppler effect derived quite a few times when the observer is moving. What is the source is also moving at some random velocity in some angle? How would one go about thinking about ...
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Doppler Cooling Limit

Can anyone help me understand this simple passage on Christopher Foot (Pg.189, Eq.9.24) about Doppler cooling: $\frac{1}{2}M\frac{d\bar{v_{z}^{2}}}{dt} = (1+\eta)E_r(2R_{Scatt})-\sigma\bar{v_{z}^{2}}$ ...
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Photon Doppler shift and Lorentz invariance

My understanding is that the energy of a photon depends your your reference frame because the energy of a photon depends on its frequency and its frequency may get Doppler shifted. Now, I am trying to ...
Nic Christopher's user avatar
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Doppler shift of light as seen by a free falling observer towards a single star [duplicate]

Consider an observer who is free-falling towards a star with no angular momentum (radial movement only considered). The velocity of the observer equals the escape velocity at each distance, but in ...
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Violation of energy conservation: cosmological Doppler-effect in what might seem an inertial frame of reference

I've seen disagreement about whether the cosmological Doppler-effect violates conservation of energy. It can be complicated to analyze since there is no reference frame of a photon. My question is: ...
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Was doppler effect for light proven experimentally?

If so, provide me with the data sources. From what I read, doppler for light is taken for granted. Or sometimes based on theoretical formulas. But if one wants to theorise, light is a mix of photons ...
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Light wave/photon doppler effect

So I understand the explanation/derivation of doppler effect from the perspective of wave crests emission being stretched out as the source moves. But how does this work from the photon point of view? ...
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Methods for calculating the orbital speed of a star in a binary system

As I understand it, to calculate the speed of rotation of a star in a binary system that is receeding, that is in the same plane as us (inclined at 0 degrees) the method is use the Doppler formula: Δλ/...
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(SPOILER: Big Bang Theory) How does this shirt Sheldon wearing, depict the Doppler effect?

This image of Sheldon wearing the shirt is from Season 1 Episode 6 of the Big Bang Theory sitcom. He goes on to demonstrate the Doppler Effect. But I don't see it. I tried thinking of it as a ...
Patrick's user avatar
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Large wavelength moving very fast or smaller wavelength moving slow

I was reading a book, which derives the final frequency due to doppler effect for sound. It states ...if the source is moving, the effective wavelength of sound will be changed... $$f' = f\left(\frac{...
Hemant Kumar's user avatar
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Symmetry and Doppler

If relativity is symmetrical (triplets moving away and returning to the center) then what happens to the Doppler effect as seen by the moving triplets? A B C A should see C moving (Doppler) away/to ...
RLH's user avatar
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What happens if you're on a spaceship accelerating close to the speed of light, but then stop accelerating?

So most people want to ask what happens if you go super-close to the speed of light and try to go a bit faster. I want to know what happens if you stop accelerating at close to $.99c$. Not decelerate, ...
Pan Asclepias's user avatar
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Is the amplitude of a wave affected by the Doppler effect?

When I search on this question online, I get conflicting answers. Most sites will tell you that the amplitude is not affected by the doppler shift, but in Einstein’s 1905 publication on special ...
Mads Vestergaard Schmidt's user avatar
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Doppler effect in QED

I am currently learning the basics of quantum electrodynamics. As I was reading through my book of choice on the subject (The Quantum Theory of Light, by Rodney Loudon), it occurred to me that it ...
slithy_tove's user avatar
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Is there a Doppler effect measured on the sunlight depending of the seasonal position of the Earth regarding the motion of the Sun through space?

The whole question is mentioned in the title but here I would add the conjecture that I am affraid that the answer(s) should be similar to a possible question about Michelson and Morley experiment...
Krešimir Bradvica's user avatar
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Do the Doppler Effect and EM Stress-Energy Tensor Imply An Object's Emitted Light Exerts More Gravity Upon You When You Are Moving Towards It?

(Please message me or comment if this is not concise enough as a question) GIVEN: Energy in the form of electromagnetic waves (aka photons) exerts a gravitational force proportional to said energy: ...
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Doppler effect on intensity of sound wave [duplicate]

The intensity of a sound wave is dependent upon pressure amplitude squared. Consider a source of power P emitting sound in all directions. An observer moving with a speed v towards the source will not ...
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Relativistic equation for the Doppler effect

From Robert Resnick's "Introduction to Special Relativity", the frequencies in two different inertial frames as shown below, are related by $$f = f'\frac{1+\beta \cos\theta'}{\sqrt{1-\beta^...
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Why do we cool atoms with laser light opposed to normal light?

When we use laser light to cool atoms, we get into some problems, because when atom beam slows down the Doppler shift changes the frequency of light in atom's frame of reference, so they can't ...
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