**294 doppler-effect questions.**

I know almost nothing about optics or lasers, but I understand mathematics. I'm trying to understand the basic principle behind a laser Doppler vibrometer, but I don't really get it. The main thing I ...

I'm reading the French Wikipedia article on laser vibrometers. With no real context, the article states that if a wave reflects off of a vibrating object, the value of the "frequency shift" is:
$$f_D ...

I calculated that the frequency of the sound that reaches a recipient
achieved when the recipient remains stationary and the source is towards him (vS = 34m / s) is not equal to the frequency of the ...

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 ...

I'm from engineering background and not firmly familiar with cosmological equations and concepts. but i know what Redshift is and how it is related to the Doppler effect.
My question is how ...

In the Doppler effect, we see that the frequency of sound that the observer hears changes according to the motion of the observer and source. For example, if the source is moving towards the observer, ...

I am little bit confused about the formula for the transverse Doppler shift( whether we use relativity or not, it isn't relevant to what I am about to ask) because I tried to derive it myself and I ...

Does time really dilate, or is it only how we perceive time, which is in the form of light waves. When an object moves away from another object at very high speeds, the light takes longer to reach it ...

I have read that the Doppler effect occurs for both mechanical and electromagnetic waves, the reason being that mechanical waves require a medium while electromagnetic waves don't.
The formula for ...

I came up with this query after @Rob Jeffries's answer to a previous question of mine.
So, is there any evidence that distant galaxies are moving away from us with speeds greater than $c$, due to ...

Derivations for the relativistic Doppler effect abound, which extends the description of the Doppler effect to include the effects of relativity in cases where the source or observer is moving at ...

According to Doppler redshift, the frequency of the EM radiation decreases if the emitting object is receding from the observer - this produces the problem in the quantisation of energy - the observed ...

$$
\begin{alignat}{7}
&& \frac{\Delta \lambda}{\lambda} & = \frac{v}{c} \\[2.5px]
&\therefore & v & \approx \frac{\Delta \lambda}{\lambda}c
\end{alignat}
$$
If you want to find ...

Say you have 2 identical LED monochromatic flashlights. The battery lasts exactly 1 hour. We are able to calculate the energy emitted as photons from the LED by Planck's Law: $E = h\nu$.
Now if we ...

I'm having trouble understanding the equation for redshift:
z = Δλ/λ ≈ Δf/f ≈ v/c
If z = v/c and c = speed of light,
how can z>1 (as nothing can exceed the speed of light)?

According to modern physics (although I don't know exactly what the theories that back it up are,) the energy of a system is conserved within a frame of reference, such as in the example ...

If a particle was travelling fast enough and had visible light shot at it, would the partice experience the light as if it was higher or lower wavelength? If so, would the particle see the incident ...

I don't understand this image:
If the stars are moving in roughly circular orbits why would red shift occur in the direction of the orbit and how would it be possible to have blue shift in two ...

Suppose, a monochromatic light source is undergoing uniform circular motion, and the observer is at the center of the circle. When the velocity of the source is perpendicular to the line joining the ...

The Doppler equation is given by
$$f_{observed} = \frac{c+v_r}{c+v_s} \cdot{ f_{emitted}}$$
Does $v_s$ refer to the velocity of the source, relative to the receiver at the time the wave (now at the ...

I am after to model the Doppler shift of an LEO satellite. At [1] (pp 183) I have found the following formula:
$$\frac{f_r}{f_s}=\frac{1-\frac{u}{c}\cos\theta}{\sqrt{1-\frac{u^2}{c^2}}}$$
$f_s$ ...

We know the formula for apparent frequency when source or observer or both are moving with uniform velocity.
But what is the apparent frequency when they are accelerating with respect to each other.

I know that the charge of objects large enough to have distinct gravity is for the most part irrelevant, but large bodies do have (at a given instant) a fixed charge, which, granted, might be hard to ...

We can detect the presence of an element in, say, a star because of the frequency of light that it absorbs which produces a line on an absorption spectrum. And we can detect relative motion towards or ...

In the book of The First Three Minutes by Weinberg, at page 21, he talks about how do astronomers measure the speed of a luminous body along the line of sight by Doppler affect, i.e. the fractional ...

Please find in the images an example from Kip Thorne’s book ‘black holes & time warps’ on Gravitational Time Dilation. I do not understand the last sentences where the doppler effect results in ...

Regarding this paper by Aleksandar Gjurchinovski,
The Doppler effect from a uniformly moving mirror
on page 4 he says that eq. (8) can be transformed into eq. (12) by the use of "some simple algebra"...

In my further reading of Special Relativity, the idea of length contraction when travelling at the speed of light is such that the length gets "squished" in the direction of travel.
This immediately ...

I have a photon with frequency $f$ in the lab frame and I observe it in a inertial frame moving perpendicular to the photon. The direction of the velocity of the photon must change, but does this ...

I am aware about the balloon expanding analogue, where the galaxies are stuck on the balloon surface and here the balloon is our space time and as the balloon expand our galaxies also go apart.
But ...

I derived an equation for the relativistic Doppler effect in the course of a routine problem: the frequency change of a photon moving in the $x$ direction, when considered a frame S' which has a ...

If i am looking at an object which is moving towards me fast enough while i am at rest, then i would see the object's color shift towards blue in the Electromagnetic spectrum. But would the same ...

I'm currently writing something that explores the phenomenon of inside jokes, in which I use an astrophysicist joke that is meant to be undecipherable to the average reader. It was recommended to me ...

Consider the situation below. I’m at a point in space along with a bunch of detector away from any gravitational field. I see a star moving away from me at a relative speed of $$v$$by measuring the ...

Let's modify a bit this question so that we use a single reference frame
Let's imagine a laser shining light on an object. Let's put the reference frame at the object. In one instance the laser ...

I have come across Doppler shift equation. If we consider the source to be moving toward the observer at a speed $V$ and observer moving toward the source with a speed $U$, for the calculation of the ...

Suppose you have a mass that is moving at relativistic speed wrt (with respect to) a powerful laser pointed at the mass. As the laser shines on the mass, assume it absorbs all the energy (and momentum)...

For the case that receiver and transmitter are moving, the shift in frequency is given with
$$f_{receiver} = f_{transmitter} \frac{c + v_{receiver}}{c - v_{transmitter}}$$
if they approach each ...

I am aware that the relativistic mass can be expressed in terms of rest mass and momentum, which seems to be the canonical explanation, but I am looking at an alternative way of visualising the ...

There are so many similarities (Doppler Effect, independence of wave velocity from source speed etc..). Try moving in your car with music and ask you friend outside record it while you moving towards ...

How does a moving sound source physically compress the waves emitted in front of it and lengthen the waves emitted behind it? Virtually all descriptions of the doppler effect provide nice visuals of ...

As defined by Wikipedia:
In physics (especially astrophysics), redshift happens when light seen coming from an object that is moving away is proportionally increased in wavelength, or shifted to ...

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 ...

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 ...

I have learned that due to doppler effect the wavelength of light increases when source is moving away from observer. Also this proves big bang theory and also universe is expanding. Like red shift , ...

Why doesn't the velocity of a photon change when it is emitted from a source moving with certain velocity? If a photon is a particle then it should have a lower velocity than one which is emitted from ...

As I learnt freq. observed by a observer from a moving source is given by $$f=f_0(1+v_s/v)^{-1}$$
If $$v_s=-v$$ f is infinity.Whats going on? Will Doppler effect will be observed if the source say is ...

On the wikipedia article (and other texts such as Optical Inspections of Microsystems) for laser Doppler vibrometry, it states that a modulating frequency must be added such that the detector can ...

Would it be practical to use doppler / laser cooling to cool a small surface (metal conductor) of 10 x 10 cm from 30 C to 20 C? Let's say using a setup like below? Where can I learn more about the ...

In Schutz's book (page 120), Schutz first derives the gravitational redshift in the PRS experiment in a previous paragraph.
$\frac{\nu^{\prime}}{\nu}=\frac{m}{m+mgh+O(v^4)}=1-gh+O(v^4)$.
Here $\nu^...

- special-relativity
- acoustics
- waves
- visible-light
- homework-and-exercises
- redshift
- cosmology
- frequency
- general-relativity
- space-expansion
- electromagnetic-radiation
- speed-of-light
- astrophysics
- photons
- energy-conservation
- electromagnetism
- relativity
- gravitational-redshift
- quantum-mechanics
- optics
- astronomy
- time-dilation
- relative-motion
- energy
- reference-frames

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