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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How can light coming from the receding galaxies be stretched like matter?

Edwin Hubble discovered in 1929 that the universe in expanding and the light from the receding galaxies are red-shifted; their wavelengths become longer. How can light which is an electromagnetic ...
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Why doesn't the acousto-optic frequency shift depend solely on the velocity of sound in the medium, if it is a form of Doppler shift?

Many optics books make the statement that the frequency shift of a laser beam from the acousto-optic effect can be thought of as a Doppler shift from a traveling index of refraction grating (pressure ...
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Doppler Effect in a video [closed]

Suppose I record a video of a vehicle moving towards me while blowing its horn, and then play the video on, say 2x. Will the doppler shift differ from when I recorded the video in the first place? ...
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Two different astronomical motions combined give a receding velocity greater than 'c' but with different effect on an observer

Let say a gallaxy is 15 billion light years away from us so the receding velocity caused by Hubble flow is more than speed of light which affects the relative motion of light towards Earth which in ...
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Is radiation pressure a doppler effect?

I came to this conclusion for the following reasons (thanks to the people who answered my recent questions): A photon pushing a mirror(*) loses energy in the form of a red shift (*through radiation ...
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Can a photon increase its frequency by bouncing against a mirror moving toward it?

As discussed in preceding questions, photons can lower their frequency after a reflection happens and radiation pressure sets the mirror in motion. I wonder if the opposite can happen, i.e. increasing ...
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Doppler effect when source and observer are in different media

According to what I learnt about Doppler effect, on moving the source and/or the observer relative to medium, there is a change of frequency heard by the observer. f(new) = f(old)(v(sound)+v(observer)...
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Difference between Doppler effect and relativistic Doppler effect?

When the source of a sound wave is moving in the direction of the sound wave it is a different scenario than if the receiver of the sound wave is moving in the direction where the sound waves are ...
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How to measure the doppler effect perpendicular to the movement in laser doppler anemometry

I'm trying to grasp the principle of Laser Doppler Anemometry. I like it as it is quite genius I'd say. However, what struggles me is the circumstance that the Doppler effect perpendicular to the ...
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Why are sonic booms produced when the speed of a sound source is HIGHER than the speed of sound?

I was recently reading about sonic booms and learned that when the speed of source is greater than or equal to the speed of sound in the medium, then a sonic boom is produced. However, I could only ...
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Why extremely distant galaxies look bigger and even more distant galaxies again smaller?

When the doppler effect reaches a certain value a galaxy looks bigger than it should be to an observrer but after a even higher value of z it again looks smaller. I will try to ask with an ...
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Doppler effect observed on pendulums

I wanted to investigate the doppler effect on pendulums and set up an experiment where: The bob of a pendulum is a speaker which emits a specific sound frequency. Directly underneath the lowest point ...
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Intuitive Explanation for Doppler effect?

I was looking for an intuitive explanation as to why the Doppler effect happens. I haven't found any, but this is what I thought: -Waves emitted travel at a constant speed -The source emits a wave -If ...
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Doppler effect when source moves with observer [closed]

I have a doubt concerning a scenario of Doppler Effect wherein the source and observer are on the same relative frame. A car is moving towards a stationary observer with speed 10 m/s. The horn has a ...
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What's the reference/original wavelength while calculating redshift?

Measuring redshift is one of the ways of analyzing distance in astronomy, since the redshift of an object is caused by the expansion of space between us and the object, the more space there is between ...
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How to apply Doppler's effect in sound when source or observer is accelerating? [closed]

Q)A parachutist jumps from the top of a very high tower with a siren of frequency 800 Hz on his back. Assume his initial velocity to be zero. After falling freely for 12s, he observes that the ...
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Frequency increase due to equivalence principle vs gravitational attraction

In Volume II Chapter 42 (on General Relativity), Feynman uses the equivalence principle to show that clocks etc. higher in a gravitational field run faster, and as a result emit photons with higher ...
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If a car scrapes a guard rail, is there doppler shift?

Doppler effects are calculated based on the velocity of the sound source. Suppose the side of a swerving car (which is moving) grinds a guardrail (which is "not" moving). Will the screech ...
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Why isn't the Doppler effect (for sound waves) symmetric with respect to source and receiver? [duplicate]

The Doppler effect formula is $$f = \frac{(v\pm v_r)}{(v\mp v_s)}f_0$$ where $f$ and $f_0$ are the observed and emitted frequency, respectively, and $v, v_r$ and $v_s$ the speed of the waves, receiver ...
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Which Doppler formula if light were to travel at non-relativistic speed?

I was going through this article about Doppler formulas and what it says is, that we only really have 1 Doppler formula, not 2. I only want if someone can confirm if I am understanding what it implies ...
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Doppler effect on non-periodic signals

I would like to understand what's happening to a signal emitted from a moving source and arriving to a moving receptor. But, when I am looking on internet about Doppler effect, I can only find ...
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How to calculate Doppler Shift for multipaths from moving objects?

Let's say we have a radar where the transmitter and receiver are placed together, and form an angle theta with a target object moving with velocity ...
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Investigating colour of a star when in motion [closed]

The star Alpha Centauri is 4 light years from Earth. For an astronaut travelling at $c/2$ from Earth to Alpha Centauri. So, this apparently means The colour of a distant star perpendicular to the ...
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Doppler effect of light when it's windy

I think I understand the classical doppler effect in sound, where the equation is non-symmetric whether the source of the observer is moving because the speed of medium where sound wave propagates is ...
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Sonic Doppler shift from a distant source

Probably most of us have heard the pitch of an ambulance change as it’s passed us, but that’s from a nearby sound source. If a sound source is far away, does the Doppler shift change? I find it hard ...
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Can we apply simple mechanics laws on sound waves

I made up a question to make you understand my doubt , see Assume that a car is travelling with speed v to a wall . When car is at distance x from wall it emits a sound signal . Find time after the ...
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Why is there a change in frequency with the Doppler effect with change in frame of reference?

If we take a source with a frequency of $230Hz$ moving at $30ms^{-1}$ right and the listener moving $25ms^{-1}$ right.Let the source be behind the listener at some distance so that the distance ...
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Doppler effect of sound in any general direction and speed

In my high school, I have been taught about doppler effect in sound, in which both source and observer are moving in same line. But I was thinking that what if these bodies were moving in any possible ...
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Why don't stars stop moving? [duplicate]

In my astro class we are learning about red/blue-shifting and I was wondering how to related to stars. So if a star is moving in some direction, the light leaving the direction of motion would be ...
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Inconsistent derivation of Doppler broadening of spectral lines

The following explications are usually made for the derivation of the Doppler broadening of spectral lines as shown in Foot (2005) Atomic Physics, sec. 8.2 (see below) Demtröder (2014) Laser ...
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The relative velocity of sound waves in Doppler effect

Let speed of sound in the medium be $v$ when the source is at rest w.r.t the medium. In the case of the observer moving towards the stationary source with a velocity of $u_1$, the speed of sound ...
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If there is any superluminal speed measured by the observer in the relativistic rocket, how does it affect the Doppler effect?

Assume that a point rocket, as well as a diode, moves with a constant velocity $v$ towards a planet on which an observer $A$ is located. (Locate the diode, rocket and $A$ respectively from left to ...
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Is the relativistic Doppler effect the only way to show that the universe is expanding?

Is there another way to show that the universe is expanding, rather then only relying on the relativistic Doppler effect?
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Doppler and Speed of light

If an an over-the-air radio signal of a certain frequency $f_c=300$ MHz travels in my direction while I'm standing still, then I observe the signal travelling towards me at the speed to light and I ...
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How to derive the Doppler shift of $v/c$?

I tried to arrive at the formula for the Doppler shift of light: $$ \frac{\Delta \lambda}{\lambda _{0}}=\frac{v}{c}$$ starting with the formula for doppler shift of wavelength $$\lambda = \lambda ...
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Centrifuge + doppler

Does the Doppler effect come into play in any interesting or useful way if a radio transmitter or receiver is spin in a centrifuge? For example, one whose radius was the same as the wavelength of the ...
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distinguishing redshift from star's color

How do scientists find out the true color of the star's light as well as the true doppler shift (relative speed)? Seems to me you wouldn't know how to separate out those 2 values.
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Terrell rotation with doppler shift on relativistic dice

Imagine a spaceship flew past Earth and at that moment it threw out a standard 6 sided dice and my ground based telescope managed to capture the atmospheric entry of the relativistic dice, I wonder ...
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What is meaning of negative frequency got from Doppler equation?

If a observer is moving away from a stationary sound source with a velocity V' then observed frequency is (1-V'/v)f where v is the speed of sound and f is the frequency observed when at rest. Now if V'...
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How are Doppler shifted absorption frequencies the same for each atom

Reading from Introduction to Nonlinear Laser Spectroscopy - Revised Edition (1988) by Marc D. Levenson and Satoru S. Kano (p13-14, bold emphasis mine): Consider a medium in which each atom can ...
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Red shift in Schwarzschild geometry

I found the following derivation of the famous red shift formula in a textbook: Let a photon be emitted radially from $r_{e}$. A stationary observer receives the photon at a radius $r_{o}$. In ...
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MTW Exercise 6.4: Doppler radar in an accelerated system. What are they asking?

Exercise 6.4 of Misner Thorne and Wheeler is: A radar set measures velocity by emitting a signal at a standard frequency and comparing it with the frequency of the signal reflected back by another ...
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Doppler effect on a WiFi [duplicate]

If we move in the universe with about 1500 km/s (earth with 30 km/s + sun with 230 km/s in the milky way + milky way....) why there is no Doppler effect on my WiFi when i change the position in the ...
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Doppler effect and time of signal change

I have a question regarding Doppler effect. Let's say the sound source is moving away from the receiver at v=c (c is sound speed) for simplicity and the the receiver keeps still. If the sound source ...
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How energy is conserved when a body moves due to differential radiation emission?

Suppose a body losing heat by radiation in the space, a white dwarf star for example. After some time its content of energy decreases by the same amount of the radiation released. But it is possible ...
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How is relativistic wavelength shift for a moving detector - stationary source explained?

Relativistic wavelength shift for a stationary source and an receding detector is given by $\frac{\lambda_s}{\lambda_d}=\sqrt\frac{{1-\beta}}{{1+\beta}}=\frac{{1-\beta}}{\sqrt{1-\beta^2}}=\gamma(1-\...
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Does the wavelength of a particle depend on the relative motion of the particle and the observer?

The de Broglie wave equation states: $$\lambda = \frac{h}{p},$$ where $\lambda$ is the wavelength of the “particle”, $h$ is Plank's constant, and $p$ is the momentum of the particle. Momentum is ...
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On conservation of momentum and doppler shift in special relativity

If a particle emits two equal frequency light rays, its momentum is conserved. But the particle has an apparent momentum change in a moving frame due to doppler shift. How can one distinguish between ...
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Doppler effect: change in properties for source and observer moving with same velocity?

If a wave source and observer are moving with the same velocity, then the movement of the wave source is supposed to result in a change of frequency and wavelength, whereas the movement of the ...
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Which type of redshift does the equation $\Delta \lambda / \lambda = v/c$ apply to?

Which type of redshift does the equation: $$\Delta \lambda / \lambda = v/c$$ apply to, that which results from the Doppler effect, or that which results from cosmological expansion? Does it even ...

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