All Questions
Tagged with faster-than-light refraction
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Speed in a medium
Let's say, that there is medium, where the speed of light is $10^8 \, \rm m/s$. So in that medium if there exists a particle that is moving through without any hindrance what would be the speed limit ...
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Why the phase velocity of X-rays inside glass is faster than $c$?
For hard X-rays the refraction index of glass becomes slightly $n<1$ which means that the phase velocity (not group velocity) of X-rays inside glass is larger than $c$ the group velocity speed ...
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Is it possible to have a medium rarer than vacuum? [duplicate]
I was wondering whether it is possible to have a medium rarer than vacuum. If that is possible then we can increase the speed of light beyond $c$. Might sound like a weird question.
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Speed of light getting lower in densed medium [duplicate]
In densed medium speed of the light gets lower so in this kind of situation is there anything which can travel quicker than light?
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How does a refractive index of less than one not violate relativity?
If I am not mistaken, this video says that X-rays travel faster in glass than in a vacuum. Special Relativity says that information can not travel faster than the speed of light in a vacuum, so what ...
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Refraction of a Ray of Light [duplicate]
Why can no medium have a refractive index less than 1? Explain with Snell's Laws of Refraction of Light.
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Cherenkov Radiation: Does it need to be faster than light in the certain medium?
I understand that when a charged particle moves through a medium and excites the atoms nearby, it produces a blue light when the atoms 'de-excite"
However, I don't understand why it has to be ...
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How does change in Temperature affect Refractive Index/Optical Density of a medium?
In my school book its stated that:
With increase in temperature, the speed of light in a medium increases, so the refractive index of medium decreases.
I read in another answer that:
Refractive ...
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Can an object move faster than the speed of light in a medium? [duplicate]
In water the speed of light changes to $2.25 \cdot 10^8m/s$. Can a electron travel faster/travel at the same speed in water. I don't see any violation of SR. So shouldn't it be possible for an ...
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Does phase velocity or group velocity change when light enters a new material? Contradictory sources
I'm so confused. I've read in this book (page 28) that group velocity of light can exceed $c$ in certain gases. However a lot of people online and in the forums say that phase velocity can exceed $c$.
...
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Is the speed of light universal for all mediums? [duplicate]
We know that the speed of light is constant in a vacuum and has the value c= 3× 10^8 m/s.
But in a medium such as glass(refractive index=1.5) the speed of light is 2× 10^8 m/s. Now considering the ...
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Does light travel faster in between Casimir plates?
Speed of light is in general $c/n$ where $n$ is a refractive index. But for example introducing two parallel plates with very small spatial separation will perturb the energy density of vacuum ...
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Can light in a medium travel faster than speed of light $c$ in vacuum?
Refractive index of medium $m$, $n_m$, is given by $$n_m = \sqrt{\mu_r\epsilon_r}$$where $\mu_r$ and $\epsilon_r$ are permittivity and permeability of the medium respectively.
And, velocity of light ...
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What is Cherenkov radiation? [duplicate]
What is Cherenkov radiation? I came across this concept when I was learning SR.
Why can't particles moving at speed of excess of speed of light in the medium. Why it does not violate the limitation ...
user221098
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How do we know that light cannot travel faster than it does?
We assume the speed of light in vacuum is its maximum speed but can we not assume that it could be faster, or slower?
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