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# 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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### Confusion about signs of the velocities in Doppler formula

Wikipedia gives the Doppler formula as: $f = \left( \frac{c \pm v_r}{c \pm v_s} \right) f_0$ c is the propagation speed of waves in the medium. $v_r$ is the speed of the receiver relative to the ...
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### Doppler effect for multiple sources [closed]

Given the figure below, how can I determine the speed from the two sources given that they both produce a frequency of 1000 Hz, and the speed of sound can be assumed to 340 m/s. The sources are both ...
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### Doppler shift from a moving reflector and source if only the relative velocity is known?

Suppose there is a device which is producing and listening to sound (sonar), a reflector is moving with respect to device and the velocity of reflector and device with respect to the air is not known, ...
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### Doppler Effect and the concept of relative velocity in GR

While reading Sean Carroll's book on General Relativity, I understood that the concept of velocity is ill-defined over large distances in arbitrarily curved manifolds, like the one used to describe ...
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### ${}$Doppler shift

If observer is moving and source is at rest then i can treat the scenario with approach in which observer is at rest and source is moving since this is what will be happening according to the observer ...
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### How does doppler cooling work?

I have trouble understanding how doppler cooling works. I understand that an atom moving towards laser sees the laser light blue-shifted and if the laser frequency is slightly below the atom's ...
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### Oscillating body and Doppler effect

Say we have a body attached to a spring, oscillating with some frequency $\nu$. This is one of the simplest problems studied in elementary Physics, and yet I've noticed we always study it positioning ...
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### Relativistic Doppler shift moving source in a circle

I am looking to understand the value for the relativistic doppler shift in the following scenario. We have a source moving in a circular pattern around a center. Now, if the observer would be in the ...
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### $I_{\nu}/\nu^{3}$ which is Lorentz invariant is also invariant for cosmological redshift?

$I_{\nu}/\nu^{3}$ is Lorentz invariant, therefore an observed intensity is boosted by $\delta^{3}$, where $\delta$ is the Doppler factor. If the cosmological redshift is same physical process with ...
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### Why do we cool atoms with laser light opposed to normal light?

When we use laser light to cool atoms, we get into some problems, because when atom beam slows down the Doppler shift changes the frequency of light in atom's frame of reference, so they can't ...