All Questions
Tagged with optics general-relativity
28
questions
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Radiation energy and momentum relation [duplicate]
Why is $\rho = 3p$ for radiation? What is the intuition behind this? If we had only 2 spatial dimentions, would it be $\rho = 2p$?
(I came across this relation while studying the state of the universe,...
- 1,161
2
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2
answers
75
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If a weak light source is attached to a string, and someone swing this light source in circle. It seems that this light source is brighter. Yes or no
It may be truly a question of life and death.
You know those glow sticks.
As a sailor it is a good idea to carry one on our lifevest.
Falling into the sea, those glow stick make a light source that ...
- 16.9k
2
votes
1
answer
173
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Huygens Principle and the bending of light
In the last section of Einstein's paper of general relativity (1916), he deduced the curvature of light when passing massive objects. It says from Huygens' principle, the light rays must suffer a ...
- 712
43
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How does gravitational lensing account for Einstein's Cross?
Einstein's Cross has been attributed to gravitational lensing. However, most examples of gravitational lensing are crescents known as Einstein's rings. I can easily understand the rings and crescents, ...
- 5,850
3
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1
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Does the index of refraction of the sun's corona and solar wind contribute to the bending of light
It's not hard to imagine that the sun's corona and surrounding solar winds have an optical density that can affect the index of refraction near the surface of the sun and bend light in these regions. ...
- 7,165
1
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Michelson-Morley interferometer in free fall
We suppose that we have a Michelson-Morley interferometer in free fall, will there be no interference: the round trip time in both arms of the interferometer is the same?
- 103k
2
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1
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282
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Do gravitational lenses act as prisms?
Light creates gravity, and the greater the light's frequency, the greater this gravitational effect is. It stands to reason then that light of different colors would react slightly differently to ...
- 804
8
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2
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336
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Why a gravitational lense makes multiple distinct pictures of a distant object rather than making a symmetric ring?
I cannot imagine how a group of galaxies may produce pictures of a distant object on a ring-like region that is not symmetric. Why there are empty parts of that ring where there are no pictures of the ...
- 103k
1
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35
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Plausibillity of using a black hole as a telescope?
I recently learned about the proposed FOCAL telescope, which would use the Sun's gravity as a lens to observe exoplanets (or whatever it's aimed at) with incredibly high resolution. Obviously, the Sun ...
- 207k
2
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76
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Transformation of the frequency of a photon after an infinitesimal coordinate transformation
I am having trouble understanding a calculation done by V. Mukhanov in his book "Physical Foundations of Cosmology". In the beginning of the chapter 9, the following arguments are stated:
...
- 350
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Does gravitation (or acceleration) make an observer see squeezed light and squeezed matter?
I read at the end of this question that Matta wrote:
"If I put a quantum field on a spacetime and boost to an accelerating reference frame then the field modes undergo squeezing which is a ...
- 207k
3
votes
2
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77
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When gravity bends light, does the light still propagate orthogonally to its $\vec E$ and $\vec B$ fields?
An ordinary photon travels perpendicularly to the direction of its oscillating E & B vector fields (i.e. $\vec{v} \propto \vec{E} \times \vec{B}$). Let's say $\vec{E}$ is oscillating "in-out" of ...
- 11.7k
3
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2
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Why do we know that light must follow a geodesic?
THE CONTEXT:
Some context to my question: Einstein once posed the thought experiment of a man falling inside a closed box. Just before the box was dropped, a photon was fired horizontally moving from ...
- 12.7k
1
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1
answer
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Physical Analogs of General relativity and optics
My Prof told me today there is a 1-1 correspondence between particles in a curved space time, and optics problems in various indices of refraction, extending even as far as black holes. Does anyone ...
- 207k
1
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1
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Direct observation of Gravitational Waves via increased resolution
First, congrats to the event horizon team for the first photograph of a black hole.
Not to downplay the significance of the photo, but it is a bit blurry. Still, it got me thinking.
One might expect ...
- 12.5k