# The velocity of light in the medium

by ENDLESSYOU
Tags: light, velocity
 P: 29 We know that light travels at the same speed in vacuum regardless of the observer.And light also travels at a speed of c/n in the medium.My question is since c/n is the limit speed in medium,then do we have the similar Lorentz transformation in the medium which just replace c with c/n? For example, suppose space is filled with medium.And the observer is in S-frame in the medium. A light is travelling in S'-frame which is also in the medium and is moving at the speed of u respect to S.Then what's the speed of light that the observer measures in S? c/n?
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P: 41,305
 Quote by ENDLESSYOU We know that light travels at the same speed in vacuum regardless of the observer.And light also travels at a speed of c/n in the medium.
c/n is the phase velocity of the light in the medium.
 My question is since c/n is the limit speed in medium,then do we have the similar Lorentz transformation in the medium which just replace c with c/n?
c/n is not the limit speed, c is. (Check out: Cherenkov radiation) The Lorentz transformations remain as usual.
 For example, suppose space is filled with medium.And the observer is in S-frame in the medium. A light is travelling in S'-frame which is also in the medium and is moving at the speed of u respect to S.Then what's the speed of light that the observer measures in S? c/n?
No. The speed measured by the observer will be the relativistic sum of those velocities (using the relativistic addition of velocity).
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P: 11,609
 Quote by ENDLESSYOU For example, suppose space is filled with medium.And the observer is in S-frame in the medium. A light is travelling in S'-frame which is also in the medium and is moving at the speed of u respect to S.Then what's the speed of light that the observer measures in S? c/n?
 Quote by Doc Al No. The speed measured by the observer will be the relativistic sum of those velocities (using the relativistic addition of velocity).
In fact, this was first observed by Fizeau in the 1850s. Of course, he didn't recognize it as relativistic velocity addition, but Einstein did, more than fifty years later!

http://en.wikipedia.org/wiki/Fizeau%...n_moving_media

P: 464
The velocity of light in the medium

 Quote by jtbell Of course, he didn't recognize it as relativistic velocity addition, but Einstein did, more than fifty years later!
Nevertheless Fizeau's experiment was a major step toward to relativity because the experiments of Michelson and Morley can not be interpreted correctly without falsification of a complete aether drag.

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