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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
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According to the postulate of special theory of relativity, speed of light is constant in vacuum. but in other media, there are particles that can travel faster
According to the postulate of special theory of relativity, speed of light is constant in vacuum. But in other media, there are particles that can travel faster than speed of light in that medium which is also known as Cherenkov radiation. So in that case, if a particle is moving with a velocity v in the direction of light, will the speed of light for that particle as frame of reference be c-v or c. Here, c is the speed of light in that medium
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Deepanshu Chaudhary
@Rubiiii mam can you go through this explanation please. According to it, electrons can travel faster. So in that case, according to the formula of velocity addition. The speed of light in that medium should be less for a particle which is moving in the direction of light in the medium. See @shanu arora mam's explanation.
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Shanu arora
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solution : here is the solution where I have consider both the cases 1) particle also in medium 2) particle in lab frame. the formule used is for finding relative velocity in relativity or known as velocity addition theorem .
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Yes. the second case is what I'm asking about. So, according to the formula, the velocity of light in that medium wrt to the particle should decrease
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yeah, according to formula the velocity decreases ,but i m not very sure of ans but approch seems to be correct and also magically when we put n=1 in the formula obtained above ,we get speed of light=c again . for n>1 it reduces.
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Ruby negi
No,, there is no particle(except tycoon which is still not discovered)having velocity greater than speed of light . Cherenkov radiation are those when light passes through a dielectric medium then the velocity of particle of light(which becomes c/Refractive index) is greater than the velocity of particle of that medium(not greater than velocity of light).. These radiations are used for discovering neutrino
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Ruby negi
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speed of light remain same in all inertial frames.. when light passes through medium then speed of light in that medium decrease and that is c/(refractive index of that medium)
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Abhishek singh Best Answer
it's phase velocity, which may exceed speed of light in some media, without violating relativity. Phase velocity is not physical. it is hypothetical (just theoretical, nothing physical), it may exceed c in media.
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Abhishek singh
Untill now, nothing physical can exceed speed of light according to Einstein's theory of relativity.
ya that's in vacuum. but in other media light slows down right.
okay, I see, what is bothering you. In any media, speed of light is c only, but if you are talking about the speed as a whole, then it appears slow, because of collisions with the partical of that medium. But in between two collisions the speed is still c.