The speed of light in any medium is dependent upon the refractive index of the medium in which it is travelling. The speed of light is more in the medium which has a lesser refractive index as compared to the refractive index of the other media. The refractive index of the glass is 1.5 and that of the water is 1.3. Light travels faster in water as the refractive index of water is less than that of glass. The refractive index of water is 1.3 which is less than glass.