# Questions tagged [speed-of-light]

The speed of light is a fundamental universal constant that marks the maximum speed at which energy and information can propagate. Its value is $299792458\frac{\mathrm{m}}{\mathrm{s}}$.

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### Time dilation and gravity

Is time dilation a by-product of an object's mass bending the space-time or is it that the presence of the mass somehow interferes with the flow of time, thereby making disturbances in it and is ...
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### Do light's electric and magnetic components oscillate in physical space?

I have heard that light is a transverse wave which is necessary for effects like polarisation, but I am unsure of what exactly this means. Is this saying that light's electric and magnetic components ...
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### Does the speed of light increase when falling?

The Schwarzschild form has a singularity at the Schwarzschild radius. If we write the metric in another form, such as the Lemaître form, the singularity disappears. In the Schwarzschild form the speed ...
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### Questions regarding action at a distance

There seems to be two concepts in action at a distance The existence of an mediating medium (energy or matter) through which action is transmitted The finiteness of the speed at which the action is ...
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### Relativistic momentum for light

In special relativity,momentum $p$ is defined by $\gamma mv$ where $\gamma=\frac{1}{\sqrt{1-\frac{v^2}{c^2}}}$. Again,we are aware of the relation $E^2=(mc^2)^2+(pc)^2$. Now,the momentum of light is ...
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### Moving at the same speed relative to electrons thus no current but seeing light being generated?

Imagine a situation where I'm moving at the same velocity as the electrons in a conducting wire. In this scenario, from my frame of reference, the electrons appear to be stationary and thus there is ...
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### Do photons moving at $c$ slow down when entering a medium or take a longer path and only appear to slow down and what happens to time? [duplicate]

Imagine a photon leaving a vacuum and entering a medium, say, air. I have 2 questions: Some claim that the photon is slowed by the medium so its speed becomes less than $c$. Is that true or does ...
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### Does Color change happen under a prism? [duplicate]

I was watching this video. It Showed that light ( green ) changes its color to red after incidence of light. I couldn't think of how this happens because light's color is dependent on frequency rather ...
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### Does light move as a wave because empty space has inertia?

If I drop a rock into a pond, a wave will propagate through the water from the location where the rock made contact. The wave will travel at a speed dependent on the density of the medium. As far as I ...
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### Is it more accurate to say space in a weaker gravitational field is contracted, or that time is faster?

Little thought experiment. An observer places a mirror and a clock 1 lightyear away from a black hole. He then goes in the black hole's gravitational field at a point where he sees the clock tick at 2 ...
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### Velocity of de-Broglie Wave

I have been trying to figure out the solution to this problem of finding the "velocity" of de-Broglie's wave. I have tried to see answers from countless sources but none of them helped. My ...
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Is there any way to know how fast would light be if it had a mass? Something like 0.000000178536 kg. At least a formula to help estimate it would help, i asked chatgpt and it said ''E = mc² E = (0....
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### Time dilation questions [closed]

If we have two reference frames K and K' which are moving relative to one another, special relativity suggests that there would be time dilation. In K, time appears to pass slower in K', whereas in K' ...
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### If a photon is absorbed, does the associated wave function disappear instantaneously, or at the speed of light?

I came to this question while thinking about light with extreme wavelengths. Say we had light (em radiation) with a wavelength of 100's of thousands of kilometres and we absorbed a photon of it on ...
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