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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CMB anisotropy, temperature and doppler effect

How would you derive the following equation: $$ T' = T_{CMB} \left( \frac{\sqrt{1-v^2}}{1+v\cos{\theta}} \right) $$ which describes how the temperature of the CMB varies due to the speed $v$ of the ...
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Relativistic doppler effect in three dimensions

Consider a sphere that travels through space with a velocity $v$. I wish to investigate the relative intensities of the CMB on all points on the sphere. For the microwaves approaching from the direct ...
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30 views

Does Doppler Effect violate Galilean relativity?

Apparent frequency when the source is moving away from the observer the relation between the frequencies is: $$f' = \frac{v}{v+ v_{s} } f$$ Apparent frequency when the observer is moving away from ...
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Cooling atoms using emitted photons from a laser cooled atom

In Doppler cooling procedure, is it theoretically possible to use the emitted photons from the target atom (cloud) to cool more atoms? The idea is to cool the atoms rapidly by using energy emitted by ...
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Doppler velocimetry accuracy

The formula is : $$v = \frac{c}{2\nu_e cos(\theta)}\Delta\nu$$ and the measured velocity is supposed to be more accurate when $\Delta\nu = \nu_d-\nu_e$ decreases. How can we see that from the ...
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Does “apparent frequency” mean the Doppler effect is not an actual physical effect?

When discussing the Doppler effect, we use the word "apparent frequency". Does that mean that the frequency of sound is still that of the source and that it is some physiological phenomenon in the ...
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Red/blue shifting out of visible spectra

How fast would a white light (emitting only visible spectra) need to travel in order to red or blue shift so far its no longer visible? Are some stars completely invisible due to this effect?
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What is meant by a “sodium line”?

What speed should a galaxy move with respect to us so that the sodium line at $589.0\ \mathrm{nm}$ is observed at $589.6\ \mathrm{nm}$? In the above question what's meant by a sodium line? The ...
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Doppler shift and special relativity

I have been listening to an audio course on Special Relativity. In the course the teacher repeatedly says that the "laws of physics are equally valid for all uniformly moving frames of reference". ...
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Why would a sweeping LIDAR or RADAR beam not produce an artificial Doppler shift?

Assuming a bi-static Radar or LIDAR with a stationary transmitter and a stationary target and a stationary receiver, with a sweeping RADAR/LIDAR beam reflecting off a stationary target: Why would the ...
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Why doesn't the speed of the wind have an effect on the apparent frequency?

A boy is standing in front of stationary train. The train blows a horn of $400Hz$ frequency . If the wind is blowing from train to boy at speed at $30m/s$, the apparent frequency of sound heard by the ...
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Beat Frequency for Police Radar with Special Relativity

"A radar speed trap operates on a frequency $v_o = 109 Hz$. What is the beat frequency between the transmitted signal and one received after reflection from a car moving at v = 30 m/s toward the ...
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Apparent frequency and wavelength in the Doppler effect

For a transverse wave(or for pressure waves required to produce longitudinal waves), the motion perpendicular to the direction of propagation of the wave is governed by an equation like $y = ...
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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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146 views

Tired light red shift hypothesis

Have there been any recent attempts to falsify the tired light hypothesis alternative to the Doppler shift explanation for the red shift, or is it simply ignored like the pilot wave quantum mechanical ...
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42 views

The Doppler shift and the apparent speed of galactic rotation with distance

A Doppler redshift would also give the illusion that galaxies were rotating more slowly then they are with the degree of illusory slowing in proportion to the degree of redshift. Do more distant ...
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43 views

Proof of expression to combine different redshifts

I am trying to arrive to the following expression: $1+z = (1+z_C)(1+z_G)(1+z_D)$ so the total redshift is the product of the cosmological redshift, the gravitational redshift and the Doppler ...
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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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How does doppler shift makes any sense?

Consider this. The reason we see red at dusk is because the sun is away from us, and thus the wave length is longer, which corresponds to the color red. But think of a transmission line that is over ...
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34 views

Is there any difference in radiation pressure for two observers in different gravitational potential?

Suppose that a light beam is shone upwards from surface of a planet. So, due to gravitational redshift, the frequency of the light perceived by observer far from the surface will be lower than that ...
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Will the frequency of the reflected wave of a moving source be shifted by Doppler effect?

I want to know if there is a moving source that emits wave to a reflecting object like a wall for example, then, will the frequency of the reflected wave be shifted because of the Doppler effect. As ...
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53 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.) EXPERIMENT A fixed source (at position $x=0$) emits brief spike ...
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45 views

How did the Huygens probe use EM waves to measure wind speeds on Titan?

In the Wikipedia's article on Huygens spacecraft, it was mentioned that one of the experiments was to measure the wind speeds on Titan by Doppler wind experiment. To quote the exact lines, it was ...
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Center of mass of two $\gamma$ rays moving in opposite directions

Suppose there are two $\gamma$ rays with frequencies $\nu_1$ and $\nu_2$ moving in opposite directions according to a reference frame $S$. I want to find the velocity of the center of mass of this ...
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Frequency of flute note heard using Doppler effect when both the source and observer are moving

Let us consider this scenario. A bicycle rider and a flute player are moving in the same direction at speeds 36 km/h and 18 km/h. The flute is producing a note of frequency 600 Hz. We need to find ...
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131 views

Transverse doppler effect in light

In most books to explain transverse Doppler effect the following example is given: Consider a source that emits flashes at frequency f0 (in its own frame), while moving across your field of vision at ...
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The supersonic bandwagon

I happen to stumble upon this intriguing animation of a Tachyon, and immediately started to think about the same phenomenon, but with sound waves. I imagined a bandwagon ...
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Could these hypothetical very long distance properties of light offer alternatives to an expanding universe or a finite number of galaxies?

Assume that there could be a property of light that it gets very gradually steadily red-shifted by traveling large astronomical distances, in exactly the same way that Doppler shift from receding ...
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What conditions should be met to notice a Doppler effect on light?

What relativistic conditions should an observer meet to notice the Doppler effect on a sample light wave, and is it even possible for one?
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Does the Doppler effect disprove the constancy of $c$? [closed]

Why doesn't the Doppler effect disprove the relativity postulate that $c$ is constant relative to all sources or observers? It seems it does because of the following example: Suppose a ship of ...
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Calculate velocity based on Doppler shift

I have a bicycle with a truck horn on it. I want to figure out how fast the bike is based on the reference frame of a stationary object watching the bike. I can use software to determine the pitch ...
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133 views

Doppler shift for a uniformly accelerating observer

This was given in textbook as an example. An observer on a spaceship with a four velocity $u$ is approaching from $x = +\infty$ a star at rest in the reference frame $S$ while undergoing constant ...
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38 views

Doppler effect for the electrons emitted from ions moving at a particular velocity

If I have ions moving in X axis (along both directions; positive X axis and negative X axis) and if I irradiate laser along the positive X axis, electron will be ejected from the ions (if I am using a ...
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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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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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Doppler effect and acceleration's impact

Can anyone explain why they say Doppler effect does not depend on acceleration? Would having acceleration not affect the frequency? If the source emits the first circular wave, moving at 50 m/s ...
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Special Relativity Question: Doppler shift

Imagine an observer watching a moving rocket carrying on it both, a light source and a clock. If on the rocket the clock is synchronized with the frequency of the light being emitted then will not a ...
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doppler shift through two mediums [duplicate]

When considering the Doppler shift, the 'canonical equation' is $$f=\frac{c+vr}{c+vs}f_0$$ However, this equation seems to run into trouble in the following situation: A light source inside water is ...
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Doppler Shift when Light Travels Through Two Different Mediums

When considering the Doppler shift, the 'canonical equation' is $$f=\frac{c+vr}{c+vs}f_0$$ However, this equation seems to run into trouble in the following situation: A light source inside water is ...
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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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Doppler effect- will frequency continually decrease?

My problems: I know that when a person is moving away, the perceived frequency will be lower than the frequency of the source. However, in the question, if the person is moving away, the ...
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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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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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Doppler shift equation results in inconsistencies

The non-Relativistic Doppler shift equation is $f = \left( \frac{c + v_\text{r}}{c + v_\text{s}} \right) f_0 $ where c is the speed of the medium (346.4 m/s for sound at 25 C temperature). I tried ...
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277 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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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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87 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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2answers
155 views

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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Does the doppler shift have any effect on the energy that the atom absorbs?

Does an atom moving towards the light that is falling on it, absorb more energy than when it is stationary? The atom should a see blue shift due to Doppler effect so the atom will see a light of ...
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201 views

Doppler effect via reflection

Suppose a police car is standing by a wall. The siren light is rotating and it will hit the wall and reflect back to the car. Does the reflected light show a Doppler effect?