All Questions
Tagged with optics general-relativity
28
questions
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43
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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
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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 ...
2
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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 ...
- 93
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. ...
- 2,270
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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?
- 1,400
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 ...
- 1,815
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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 ...
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
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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 ...
- 708
3
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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 ...
- 945
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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 ...
- 1,087
1
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1
answer
96
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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 ...
1
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1
answer
42
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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 ...
- 121
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62
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Fermat principle [closed]
According to Fermat's principle, the actual path taken by a light ray in space locally minimizes the "optical length". It is possible to use the optical length (for some given function n) to defined ...
- 61
-3
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5
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411
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What causes a single photon to divert its trajectory?
If a single photon passes close enough to a star, the gravity will diverts its trajectory. What causes a photon to divert its trajectory as it passes a sharp edge or the boundary of two mediums?
- 4,083
3
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80
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Critical angle in General Relativity
Analogies between optical propagation in different refractive media and the effect of gravity in light geodesics are well established. But in optics one can have total internal reflection if certain ...
- 14.5k
7
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2
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How do we know that bending of light around stars is due to bending of space-time and not diffraction?
One question that popped up during the studies of special and general relativity (which I am forced to take unfortunately) is the following:
How do we know that this is due to the bending of space-...
- 649
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1
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104
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Effects of the sun on Einstein's prediction of gravitational bending of light
From what I understood, $1.75''$ was the predicted value derived by Einstein.
Is it possible that light from the star, at the time of solar eclipse, can also be bent somehow by the solar particles ...
1
vote
1
answer
808
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Treating gravitational lensing as index of refraction
In Einstein's theory of gravity, an electromagnetic wave passing near a massive object is bent from its rectilinear path. We may regard this bending equivalently as due to a medium of refractive index ...
- 1,116
1
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1
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42
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Black holes in a denser media
In Crown Glass, the speed of light is 1.52 times the speed of light in vacuum. Consider the following hypothetical situation:
Hypothetical Situation
If a black hole is surrounded by a giant crown ...
- 359
4
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2
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421
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Seeing one's back on the event horizon
If we would hypothetically be exactly on the event horizon, we should see our own back, because of the circular motion of photons on the event horizon, right?
But what would be the image size, or $-$ ...
- 991
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1
answer
311
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does the beam of a laser have 'throw'?
I was thinking about Einstein's train and platform experiment and was wondering if a beam of light experiences throw? Let me explain, if I take a water hose and point it straight out and then swing ...
- 93
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1
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344
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Book on optics in curved space-time
As evidenced from my earlier questions on vision and curved space, I am struggling a little bit with visual perception in curved space-time.
I would like a book recommendation on optics and vision in ...
2
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2
answers
563
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Does gravitational lensing violate Fermat's Principle that light must travel in straight lines?
Does bending of light due to warping of space violate Fermat's Principle or is it that in the principle light goes in a straight line with respect to space (taking space as the reference) and in ...
- 3,905
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2
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312
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Gravitational distortion of an object's diameter, at a distance,
Does the curvature of space-time cause objects to look smaller than they really are? What is the relationship between the optical distortion and the mass of the objects?
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3
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Liouville's theorem and gravitationally deflected lightpaths
It is customary in gravitational lensing problems, to project both the background source and the deflecting mass (e.g. a background quasar, and a foreground galaxy acting as a lens) in a plane.
Then, ...
- 3,755
43
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5
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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, ...
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