A. True
What is refractive Index?
Refractive Index is  calculated from the ratio of the speed of light in a vacuum to that in a second medium of greater density.
The equation is n=c/v.
In water, the refractive index is 1.3 and in glass, it is 1.5.
Therefore,
Light travels faster through water, than it travels through glass.
As the refractive index of the medium increases, the speed of light in the medium decreases.
The refractive index of glass is higher than air, so the speed of light will be slower in glass and faster in air.
Some charged particles can move faster than in water and therefore travel faster than light.
Learn more about Refractive Index here:
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