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 we extract the Doppler shift of supernovae?

My understanding is that supernovae are used as standard candles, whose spectral lines indicate the recession velocity of the host galaxy. But the material from the supernova is ejected at a ...
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From the point of view of a moving source of light, is the wavefront always a sphere with them at the center?

Most diagrams regarding relativistic doppler effect always show in terms of an outside observer that is looking at both the light and the moving source. In this context, yes, the source moves towards ...
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Relativistic Doppler Effect: Intensity change

My physics prof. mentioned briefly, that in the framework of the relativistic Doppler effect, not only the frequency (alternatively, the wavelengh) changes when objects move with respect to each other ...
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Doppler shift in period of a pulsar

The paper Discovery of a Pulsar in a Binary System says that the reason this pulsar's period is not constant in time is due to Doppler shift from the pulsar's orbital motion. I am accustomed to ...
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Redshift Due to Expanding Space (not increasing distance) [closed]

Please NOTE: "For example, a question that proposes a new concept or paradigm, but asks for evaluation of that concept within the framework of current (mainstream) physics is OK." And: "...
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Why is it commonly stated in textbooks that no preferred inertial reference frames exist? [duplicate]

According to formulations in most textbooks, the principle of relativity states that the laws of motion are the same in all inertial frames, that all inertial frames are equivalent, and that no ...
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Consider a light source moving at a high velocity. How all does relativity affect the brightness, wavelength, and other attributes?

Consider a spherical light source moving at a high velocity (v=.9c) straight towards you, the observer. How all does relativity affect the brightness, wavelength, and other attributes of the light ...
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If light from a moving emitter has doppler effect would a laser used on Earth show that?

If light from a moving emitter has doppler effect would a laser used on Earth show that? Will the laser have 2 different frequencies when pointed in 2 opposite directions on Earth due to Earth's ...
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Does a blueshift mean that time goes faster?

This is a follow-up question to this answer. The assumption in this answer is that time dilation always causes a small redshift when an observer looks at an object moving at a significant fraction of ...
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Measuring the speed of light using Doppler Effect? [duplicate]

Could it be possible to measure the speed of light using the Doppler effect of light? I would propose an experiment where a light source is moving towards a photo detector at a constant speed, due to ...
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What would Planck's law become if derived from Doppler shifted wavelengths?

Derivation of Plancks law does not involve Doppler effects on wavelength. What would Planck's law become if derived from Doppler shifted wavelengths?
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Doppler Effect of Stars

To measure the velocity of a star (away from us), we use its Doppler redshift. However, a redshift may be a result of other factors, such as different gravitational potential (which is always the case,...
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Transverse Doppler Effect In Special Relativity [duplicate]

Based on the Wikipedia article for special relativity: It shows how light is red or blue shifted based on whether the observer is moving or the source is moving. I'm having a hard time understanding ...
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Doppler formula derivation using wave-vector and 4-velocity

I am studying Special relativity by myself using Rindler, while is was doing some questions of the book one in particular it's not clear to me if my answer is right, is this one (i) If a wave train ...
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What is the formula of Doppler Effect for moving source and moving observer with an angle?

The Doppler effect equation is: $$f_{\text{observer}} = f_{\text{source}} \left( \frac{v \pm v_{\text{observer}}}{v \pm v_{\text{source}}} \right)$$ where we take the velocity positive when it is from ...
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Why didn't I experience violet shift at traffic signals?

context: we were studying sound waves and our instructor informed us about doppler effect and violet shift of light. Now I have many times exceeded the speed limit at night where there were no cameras ...
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Cancelling out Doppler Effect and Relativistic Time Dilation

Let, Alice is moving towards Bob. Relativity will cause Bob's time dilate with respect to Alice, on the other hand Doppler Blues Shift means that signals sent by Bob at 1 second interval will reach at ...
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Doppler Effect and Relativity paradox

Let, Alice is moving towards Bob at very high speed. Therefore, events in Bob's frame will appear to happen slowly in Alice's frame due to time dilation. Since velocity is relative, the same is also ...
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Can a laser-pumped laser cavity be laser-cooled by its pumping laser (and pump its pumping laser in return)? Is remote-cooling possible outside a lab?

tl;dr: Can one laser "suck" heat from another one (e.g. via Doppler-cooling, but not limited to that) hence remote-cooling it? I haven't found any non-paywalled literature on the ...
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Does Redshift depends on wavelength?

I came across this equation on Wikipedia: $$z=\frac{\lambda_{\text{observed}} - \lambda_{\text{emitted}}}{\lambda_{\text{emitted}}}$$ and it got me thinking: If I measure a wavelength of $700 \;\text{...
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Is red-shifting the only proof for the expansion of the universe?

Are there other proofs for the expansion of the universe other than red-shifting? If yes, what are those? Thank you.
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If traveling with relativistic speeds can observer find space denser than normal?

I know that outer space contains few particles per cubic meter, but I am curious if travelling that fast for our brave traveller all of these particles will look like a dense pool of molecules. And ...
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A doubt on Doppler's Effect [closed]

I was solving a problem based on Doppler's Effect The Question is : A car is moving towards a stationary observer with speed 10m/s . The car blows a horn of frequency 640Hz for 10 seconds . If speed ...
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What is the difference between observer moving and source moving in affecting the sound signal? [duplicate]

Why can't we solve all the doppler effect problems for sound in frame of source instead of observer moving using relative velocity. I want to know why this method does not work?
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Doppler Effect formulas for stationary observer and source [duplicate]

I am a high school student and recently learnt about the doppler effect. My teacher showed me two different formulas for the doppler effect with moving observer and moving source. Why are there ...
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In doppler effect derivation why are the considerations for source moving different from that of observer moving?

I've looked through the derivation of doppler effect in 2 cases ( source moving and observer moving).. Why can't we solve all the doppler effect problems in frame of observer and assume it is at rest?
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Relative motion between a light source and a stationary observer

I've been taught that for a stationary observer moving at constant relative velocity away from a light source, this light source will decrease in frequency as the distance between the two increases. I ...
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Does the observed wave speed change if the observer is moving towards the source?

We have the formula for the perceived frequency with a moving observer as follows: Therefore, the perceived frequency does change for the observer. Also, my textbook (Physics for the IB Diploma ...
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Redshift is same as Doppler effect in sound ? if not how different it is?

Is redshift same as doppler effect in sound ? if not what makes it different ?
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Is speed of sound same for all inertial frames?

For instance: In the diagram below suppose A shouts at B who is at a distance of S apart while the platform moves in a uniform velocity V1. If the speed of sound in air at *rest is V, wouldn't the ...
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Relativistic doppler shift

When rearranging the doppler shift equation in terms of wavelength to get in terms of $\beta$ we get: $\beta = \cfrac{(\lambda_{source})^2-(\lambda_{obs})^2}{(\lambda_{source})^2 + (\lambda_{obs})^2}$....
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Is there cosmological redshift within the Milky Way?

Cosmological redshift is based on the idea that the universe is expanding. When the universe doubles in size, or scale factor, the wavelength of light doubles. But the Milky Way is not expanding so my ...
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What is effect of relativistic speeds on blue and red objects?

We know, As per Doppler effect, if an object travels with speed close to that of light, if appears red if it goes away from observer and it appears blue if it comes towards the observer. My question ...
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Interpretation of this spacetime diagram for freefalling observers in Gullstrand-Painleve coordinates?

The following diagram (which I've adapted from Chapter 7 of "Exploring Black Holes" by Taylor, Wheeler & Bertschinger) shows the radial world-line of a free-falling observer into a ...
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Can cosmological redshift be explained purely by the relativistic Doppler effect? [duplicate]

I want to preface this by saying I don't disagree with the idea of the universe's expansion, this was just a random thought that popped into my head. I also apologise in advance if it's a duplicate, ...
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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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1 answer
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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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1 answer
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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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1 answer
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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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2 votes
1 answer
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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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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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1 answer
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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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2 answers
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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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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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