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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Does the energy of a photon change in different inertial systems? [closed]

Given a photon with energy $E$ is some system S what would be it's energy in a system S' with a constant velocity v relative to S? I have no idea where to start from. I think you need to calculate the ...
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Transverse Relativsitic Doppler Effect

I have a question regarding relativistic Doppler effect. The following page is taken from "Introduction to Special Relativity" by Robert Resnick. My question is why Eq. (2.25b) needs to be ...
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Doppler Effect in Slow Light

As experimentally slow light is possible, i.e. light at or near speed of 20m/s. So suppose observer in room with slow light moves faster than slow light then would they be able to experience doppler ...
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A problem related to Doppler Effect

Will Doppler Effect of sound waves be observed if the waves are observed from a frame that is moving with a constant velocity with respect to the frame in which the waves are being produced ( where ...
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Limit cases for the Doppler effect

When considering a wave emitting source and an observer that are in relative motion, one usually chooses between the classical Doppler effect and the relativistic Doppler effect depending on the ...
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Is the cosmological Doppler effect more effective at long wavelengths?

When observing the Doppler effect of a particular galaxy, is the wavelength change greater for long wavelengths? According to the simple Doppler effect formula, the wavelength change is proportional ...
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Could Mars be used to measure the one-way speed of light? [duplicate]

I just watched this Veritasium video, explaining the difficulty of measuring the one-way speed of light. The presenter explains that a round-trip will always average out to $c$ even if the speed in ...
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Transverse doppler effect paradox

When observer sees source in actual nearest position, there is a transverse Doppler effect due to time dilation. From the view point of observer, the source experience a shorter time by $1/\gamma$, ...
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How are satellites tracked using Doppler Shift?

I need to understand how Doppler Shift is used to track satellites in LEO, (research papers also appreciated)
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What would the wavelength be in this Doppler effect example?

I'm trying to understand an example of the Doppler effect. Let's say we have an object moving at $100 \ \dfrac{\text{km}}{\text{h}}$ ($27.7 \ \dfrac{\text{m}}{\text{s}}$) and emitting a frequency of $...
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Some confusion in Doppler effect in accelerated motion

I am sharing two solved questions based on Doppler effect in Accelerated motion .Although I have understood the methods for both the questions , I wanted to know what is the difference between the two ...
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Thought experiment with doppler effect [closed]

So I want to start with a thought experiment imagine one observer moving at a speed of 299 792 457,9999..9 (twenty 9s) assuming c=299 792 458,0 and he emmits a ray of xrays to the moving direction so ...
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Relativistic Doppler Effect of light

Is the formula of the non-relativistic doppler effect of light a limiting case of the relativistic doppler effect?
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Using an LED for Doppler cooling

Would it be possible to use an LED to perform Doppler cooling? I understand that the linewidth of lasers is around a tenth of LEDs. I feel that there should be a trivial reason that should explain the ...
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If the only way to observe a tone generating object is by listening, can a distinction be made whether the object, the listener, or the air is moving?

Although most commonly associated with a moving object emitting a tone (like a car or train), a sound may also be doppler shifted if the listener is moving or (even less obvious) if the air medium is ...
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Does velocity of source affect the duration for which the observer hears the sound?

If the source is moving, the wavelength of sound in air changes but does it change the duration for which the stationary observer hears the sound? Like say if the source moving at velocity $V$ emits ...
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Gravitational wavelength shift of microwave background radiation

I can't find this precise question answered. It is basically a two part question. Would the microwave background radiation, as well as light travelling to us from stars in an expanding universe ...
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Apparent wavelength received by observer in doppler's effect

I have a few doubts about Doppler's effect. Does the apparent wavelength received by the observer depend upon whether the observer is moving or not? $λ_{apparent}=\ \frac{v_{sound}\pm v_{source}}{f}$....
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Doppler effect formula when the medium is moving

We know the basic formula of apparent frequency in Doppler's effect. $f'=\frac{v_{sound}\pm v_{observer}}{v_{sound}\pm v_{source}}f$. What do we do when the medium itself is moving, say with a speed $...
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Why is there a Nyquist limit in pulsed-wave doppler ultrasound?

The Nyquist limit represents the maximum Doppler shift frequency that can be correctly measured without resulting in aliasing, and always equals the Pulse Repetition Frequency (PRF)$/2$. However why ...
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Could photons eventually turn into black holes according to an observer traveling faster and faster towards the light source due to blue shift?

The following question was answered and the answers do make it seem like photons with a high enough frequency, could, in theory, turn into black holes: How much energy does a photon need to form a ...
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Calculating redshift from distant galaxies using spacetime metric

In Sean Carroll's GR book, pg. 104, it was said that at a rigorous level, the notion that galaxies are "receding away from us" at a speed defined by their redshift is nonsense, since ...
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If a very distant supernova has a high Doppler effect redshift do our eyes see its evolution picture like in 'slow motion'?

If a very distant supernova has a high Doppler effect redshift do our eyes see its evolution picture like in 'slow motion'? If a same type of supernova apparently lasts longer if it has more ...
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How does medium affect the asymmetry of doppler effect in sound?

Firstly I would like to point out that I have seen several answers on the stack community similar to my question, however, I feel I haven't understood it quite yet Doppler effect in light only depends ...
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Do humans use the doppler effect to localize sources of sound?

Consider a source of sound such as a person speaking or a party of people which makes a continual drone sound of the the same frequency. If a human shakes their head side-to-side with sufficient ...
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Neutron star emition of light: Are photons somehow fighting against gravity while leaving the surface?

When a source is receding from the reciever the wavelength is elongated as the light is emitted from a more and more distant point so a distant rotating galaxy has two differently coloured parts ...
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Relativistic Doppler effect for parallel-moving observers

Suppose two observers (A, B) are moving along trajectories parallel to the x-axis in some inertial frame. Now A emits a photon with $\nu_a$ in the positive y-direction, which is recieved by B with ...
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Why doesn't source affect sound's speed in doppler's effect?

In the derivation of the doppler's effect formula $$f_{app} = f\frac{v ± v_{observer}}{v ± v_{source}}$$ ​It is assumed that the speed of sound is unaffected by its source's speed (i.e it's the same ...
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In empty space what happens to the lights energy that is lost to the doppler effect go to? [duplicate]

When light makes a long distance journey it's frequency shifts toward longer wavelengths. With $E = hc/\lambda$ being the amount of energy in any given photon (see photon energy); as it travels trough ...
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Doppler Effect and Radar Sensors

Radar sensors make use of the Doppler effect to measure the radial velocity of an object. The radar's Tx antennas emit an electromagnetic wave which travels to the moving objects, is reflected and the ...
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How is speed of Milky Way determined relative to CMB dipole?

I read that our galaxy the milky way is moving at approx 630km/s relative to CMB dipole, I think they applied Doppler shift to find this number but how do they do that? I know when universe is a hot ...
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What is the “Doppler mismatch”?

In the paper Coherent Optical Detection of Highly Excited Rydberg States Using Electromagnetically Induced Transparency. A. K. Mohapatra, T. R. Jackson and C. S. Adams. Phys. Rev. Lett. 98, 113003 (...
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Momentum of a relativistic atom

I have been solving a problem where you should derive the formula for doppler effect when a source of light is an atom moving at a relativistic velocity v. I understood everything in the solution ...
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Do gravitational lensing experience Doppler effect?

I watched dark matter explained by Perimeter Institute on YouTube and they used it as gravitational lenses, they also explained Doppler effect so we know how fast things are relative to us. I wonder ...
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Two cars are moving away from each other. what is the frequency heard by observer in one of the car if the other blows a horn? [closed]

The cars are moving with same velocity in the opposite direction (one going south and the other is going north)
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Why is there “red/blue shift” instead of “light/dark shift”?

In physics class today we were learning about the doppler effect for sound, and the teacher said that blue-shift and red-shift are the exact same thing but for light. This does not make sense to me. ...
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Two photons Rabi oscillation

Assuming we have a 2 level system (e.g. an atom with 2 energy levels) and the lifetime of the upper level can be neglected, if we make the atom interact with a laser at a fixed frequency, we would get ...
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Would Radio Communications Between Parties Experiencing Time Differently Be Compressed/Stretched

This is a contrived and extreme example that is likely not even possible, but I'm hoping the answer will help me understand something about communications across relative time. Imagine two individuals ...
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Applying Doppler's effect when both source and observer are same

I was solving this question that describes a situation where a train is moving towards a stationary object and the driver hears the reflected sound. My thought My ...
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Doppler effect preserved during reflection by transverse moving object

I have been looking through the web for an answer to my question, but even those topics on stackexchange do not really specifically answer my question. So, I would like to learn if the doppler shift ...
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Orbital quadrature and relative velocities

In Robert J. Sawyer's sf novel The Oppenheimer Alternative, a bunch of physicists try to find the composition of the martian atmosphere with spectroscopy. They say that to find water vapour or oxygen, ...
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Doppler effect of observer and source moving in different directions and at an angle

While studying the classic Doppler effect equation, I was curious to how the traditional equation of the doppler effect for sound, where the observer and sources are facing each other, gets effected ...
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Reflection of light from a moving mirror with Lorentz-transformation

The trajectory of a moving mirror at speed $v\geqslant 0$ is given as $$s(t) = s_0 + vt.$$ A plane-monochromatic wave emitted from $x=0$ at $t=0$ with frequency $f$, given by $$\mathcal{E}(x, t) = \...
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Doppler effect and Lorentz transformation

At time $t_0 = 0$ someone on earth sends a (frequency modulated) signal to a spacecraft, which is at distance $R$ and moves with speed $v \geqslant 0$ along the $x$-axis. Suppose the signal is ...
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How abruptly does the Doppler shift change sign?

(For context, I originally thought of this question in the context of electromagnetic Doppler shift, but I'm also curious if the same logic applies for acoustic Doppler shift.) Assume you are watching ...
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Variation of Intensity when a source moves

When a sound source moves, frequency perceived by the observer is changed due to the doppler shift. Does this apply to intensity too? If yes then how. Thanks!
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Data for experiments of Doppler effect

I am a high school student that has attempted to carry out the experiment for the Doppler effect using an RC car going at constant speed, a sound source at constant frequency and phyphox app to ...
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Why is the sound produced by a sonic boom low pitched?

According to Doppler's effect $$f'=\frac{v+v_0}{v-v_s}f$$ where $f'$ is the observed frequency, $f$ is the actual frequency, $v$ is the velocity of sound waves, $v_0$ is the velocity of the observer ...
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Doppler as an eigenvalue of the Lorentz transformation

It is a known fact that $$ \gamma (1\pm\beta) = \sqrt\frac{1\pm\beta}{1\mp\beta} $$ is an eigenvalue of the Lorentz transformation (which is a linear transformation). This is also (as stated in the ...
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Working principle of echo sounder

An echo sounder is simply a device that is used to help sailors determine the depth of water at different locations in the sea. There is a transducer that is attached to the hull of the ship that ...

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