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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Why doesn't the motion of a car affect the frequency of radio stations?

When we go in a car and tune to an FM radio station, why doesn't our motion disturb the frequency? Like the Doppler effect?
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Can gravitational waves be red-shifted?

Whenever the Doppler effect is mentioned, it's typically in the context of sound waves or electromagnetic radiation. On the cosmological scale, red-shifting is also important because of the enormous ...
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Relativity of temperature paradox

The imagined scenario: Part A: From special relativity we know that velocity is a relative physical quantity, that is, it is dependent on the frame of reference of choice. This means that kinetic ...
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Why do lines in atomic spectra have thickness? (Bohr's Model)

Consider the atomic spectrum (absorption) of hydrogen. The Bohr's model postulates that there are only certain fixed orbits allowed in the atom. An atom will only be excited to a higher orbit, if ...
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Could I see the cosmic microwave background if it were Doppler shifted enough?

If I traveled fast enough, my current understanding is that visible light would be blueshifted to the blue/UV range, but also that microwaves and longer wavelength waves would be blueshifted into the ...
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What are the characteristics of light entering a disk spinning at near $c$?

If I were to spin a translucent disk so that the edge is spinning at .9c and shoot a laser beam at it perpendicular to the edge, what would happen to the light as it travels in one end of the disc and ...
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Hearing a sound backwards because of Doppler effect

Consider a supersonic plane (mach 2) aproaching a stationary sound source (e.g a fog horn on a boat). If I understand it correctly, the passengers in the plane can hear the sound twice. First at a 3 ...
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398 views

How is the Photoelectric Effect affected by Blue-Shifting

I was thinking about the Photoelectric Effect and Blue-Shifting when I came up with a thought experiment that I couldn't think of an answer for. The thought experiment is as follows: A metal plate is ...
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Blue-shifting as opposed to violet-shifting

A recent XKCD comic implies that the sky is blue as opposed to violet due to human physiology, and that animals more sensitive to shorter wavelengths will perceive the Earth's sky as the shortest ...
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288 views

In terms of the Doppler effect, what happens when the source is moving faster than the wave?

I'm just trying to understand this problem from a qualitative perspective. The Doppler effect is commonly explained in terms of how a siren sounds higher in pitch as it is approaching a particular ...
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Question on luminosity of a radiant source and its dependence on temperature, and involvement of Doppler Effect

A few days ago, I happened to go through the chapters on Radiation, and Photometry, studying them at quite an elementary level. I studied Wien's displacement law, and the dependence of luminous flux ...
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How do you measure distance to stars within the galaxy?

I know that for close by stars (<50 LY) we can use the parallax effect. And for distant galaxies we use red-shift (& hubble's constant). So how do we measure how far is a star lets say 50,000 ...
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How does the Hubble Redshift work?

I am a little confused about the workings of the Hubble Redshift. I do understand the classical Doppler-effect, however in special relativity the velocity of light c is a natural velocity limit. So ...
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285 views

Would cosmological redshift be present in the following situation?

I'm trying to understand if cosmological redshift is just a secondary form of doppler redshift, or something else entirely. Suppose the two galaxies in the picture are receding from each other, but ...
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Meaning of negative frequency of sound wave

Suppose that Alice and Bob are both holding speakers emitting sound at a frequency $f$. Alice is stationary while Bob is moving towards Alice at twice the speed of sound. In the case of Alice, if I ...
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2answers
240 views

Redshifting of light from a moving light source

We know that the expansion of space causes redshifting of light. I even read somewhere that the Doppler effect also happens in light. So imagine I switch on the headlights of my car in front of a wall....
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201 views

Wave equation for sound waves and moving source

Is there a way to take a moving source already into account when one derives the wave equation for sound waves and derive from that using only math the Doppler effect for moving sources?
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199 views

Doppler effect and light

Approaching the speed of sound in an aircraft is relatively difficult, because the closer you get to Mach 1, the denser the pressure is around you (sound accumulates causing vibrations). Is there a ...
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197 views

How would I perceive a purple ball when traveling at relativistic speeds

I have a 'thought experiment' which I'd like to ask about. I was thinking what speed I would have to drive towards a crossing to see a red light as a green light - pretty easy, using the doppler ...
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Sound frequency of dropping bomb

Everyone has seen cartoons of bombs being dropped, accompanied by a whistling sound as they drop. This sound gets lower in frequency as the bomb nears the ground. I've been lucky enough to not be ...
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What happens to sound at speeds greater than mach 1? [duplicate]

We know that a moving source of sound waves produces Doppler shift, so that sound waves are closer-together in the front and farther apart behind, creating a difference in pitch. Let's consider a ...
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422 views

Relativistic Doppler effect on gamma rays

I'm trying to solve the following problem : An electron-positron pair annihilates, creating two photons. At what speed must an observer move along the line of the photons in order that the ...
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quantum explanation of doppler effect

How would quantum mechanics explain doppler effect? And just for curiosity, is there any effect similar to doppler effect occuring at quantum level?
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64 views

Effect of motion of medium on frequency

Will the frequency observed by a stationary observer will remain same if only the medium between the source and observer is moving?(ie. both source and observer are at rest and wind is blowing from ...
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Finding the cosmological redshift of a galaxy in the expanding Universe

Firstly, I understand what the Doppler effect is when it comes to sound or light waves. From everything that I've read, we are told that the universe is constantly expanding since the all the ...
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Does time dilation correct for the Doppler effect?

Knowing that a body in motion experiences time dilation, "also" knowing when two objects travel at a great speed away from one an other, both observers experience the others clock as moving slower ...
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Why same formula describing Doppler effect in the case of light in different situations?

I made comparison between Doppler effect in light and sound and one interesting thing that I saw was that in the case of sound there are different formulas to find the apparent frequency in different ...
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If I'm running away from chasing gamma photons, I can see them, right?

Suppose Bruce Banner goes back in time, convinced that the Hulk is a stupid menace. Let's say he also borrows Quicksilver's speed abilities (maybe the Flash is more appropriate, but based on the ...
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The Equivalence principle of General Relativity and the Doppler Effect

I am studying General Relativity and am trying to understand the Equivalence Principle more thoroughly. Basically, it is said that if you are in a uniformly accelerated frame of reference in free ...
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A Doppler Effect problem with a moving medium

I tried solving the following question and started having multiple doubts: Two cars A and B are moving towards each other with some speed $25$ m/s. Wind is blowing with speed $5$ m/s in the ...
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366 views

Bending of light from a moving light source

First I will have to explain my question. Look at the image below. This shows doppler shift when an object is moving horizontally to the direction of the wave. Keep the word 'horizontally' in mind. ...
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Sounds of supersonic objects

Would you, as a stationary observer, hear a sound in reverse when the source of the sound travels with twice the speed of sound? Of course, he wouldn't hear anything at all before the airplane passed ...
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Relativistic Doppler effect derivation

This is about a step in a derivation of the expression for the relativistic Doppler effect. Consider a source receding from an observer at a velocity $v$ along the line joining the two. Light is ...
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103 views

Is there a way to create a flickering frequency to be dependent on speed of the person looking at it?

Is there a way to make a screen or a road sign flash at different rates, depending on the velocity of the observer looking at it? I would like to achieve a state where two observers going at ...
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Curious question about light and photons

If a photon wavelength (e.g., yellow) is isolated from the other wavelengths that the sun emits (once it gets to earth), can that particular particle/photon be distorted slightly into a wavelength ...
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Is there any way to differentiate between a redshift caused by recessional motion vs. gravity?

How certain, if at all, are astronomers that the redshift they are measuring is relating to recessional motion as opposed to gravity?
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Conservation of energy (or lack thereof) in Doppler cooling [duplicate]

I did not find my question answered elsewhere, so here it is. I'm doing a project in my first optics course, and we are reading a bit about Doppler cooling. I understand that a laser is tuned to a ...
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2answers
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Is it better to call the doppler effect a change in wavelength or frequency?

Why is it preferable to say that the doppler effect causes a shift in frequency rather than a shift in wavelength? I often read on websites that they define the doppler effect as a change in frequency....
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Why did we need relativity to derive $E=mc^2$?

Okay, so the way I understand one of the "derivations" of $E=mc^2$ is roughly as follows: We observe a light bulb floating in space. It appears motionless. It gives off a brief flash of light. We ...
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Will a warm body naturally slowdown?

Suppose a warm body moving in an empty space with high speed. The body emits radiation based on its temperature. The protons emitted forwards of the body will have higher energy due to Doppler shift ...
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'Doppler redshift' Vs 'Cosmological redshift'

It is not difficult to understand the differences between 'Doppler redshift' and 'Cosmological redshift' conceptually. But how do astronomers distinguish them when doing observations?
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Doppler cooling limit vs recoil limit

I was discussing laser cooling in class today and I understood that the main principle of the process is to tune a laser to a frequency lower than the absorbtion frequency of the atom and so only the ...
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Doppler effect of sound waves

I am looking for interesting ways to introduce the Doppler effect to students. I want some situations in nature or every day life, where a student is possibly surprised and may ask "how could it be"? ...
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283 views

Is the Doppler effect for sound symmetrical for observer or source movement?

It makes intuitive sense to me for the apparent frequency of a sound as modified by the Doppler effect to be based entirely on the speed at which the observer and the source get closer or farther ...
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Doppler shift and Galilean relativity

Doppler shift has different forms if the observer or the source are in motion. I consider Doppler shift in the case of sound. I tried to find an answer on the non symmetry of Doppler effect, ...
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242 views

Doppler Effect: What is formula for Rate of Change of Period observed by accelerating receiver?

(I have looked at other questions relating to Doppler Effect with acceleration but none seem to provide the formula in question.) Edit: I wish to avoid using the Einsteinian relativity model. So ...
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Are photons absorbed by expanding space?

Can a photon/EM-field-excitation redshifted by spatial expansion be completely dissipated? Does the energy reach a minimum value (Planck's constant) and continue on as normal? Does expansion also ...
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How many boats does it take to find an acoustic buoy by Doppler shift?

Inspired by this question on the Doppler shift, suppose there is buoy somewhere on the surface of the ocean emitting a pure frequency. You get to place some boats wherever you want on the surface of ...
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1answer
302 views

With respect to the doppler effect, are pitch changes sudden or gradual?

Before reading the below content, it is important to read the final note at the bottom first. Take this excerpt from Wikipedia regarding the Doppler effect: if the siren approached the observer ...
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About the standard derivation of the gravitational redshift

The objective is to derive the gravitational redshift ONLY from the Einstein's equivalence principle (E.E.P.), without using the whole theory of Relativity. This is the standard "informal" derivation ...