The refractive index of fused quartz is 1.46 and that of sapphire is 1

The refractive index of fused quartz is 1.46 and that of sapphire is 1.77. If vq is the speed of light in quartz and vs is the speed of light in sapphire, then which one of the following relations is correct ?

”v<sub>q</sub>
”v<sub>s</sub>
”v<sub>s</sub>
”v<sub>s</sub>
This question was previously asked in
UPSC NDA-2 – 2020
The relation vq > vs is correct.
The refractive index (n) of a medium is inversely proportional to the speed of light (v) in that medium, according to the formula n = c/v, where c is the speed of light in a vacuum. Therefore, v = c/n. A higher refractive index means a lower speed of light, and a lower refractive index means a higher speed of light.
Given nq = 1.46 and ns = 1.77. Since ns > nq, it follows that vs = c/ns must be less than vq = c/nq. Hence, vq > vs. The speed of light is slower in sapphire than in fused quartz because sapphire has a higher refractive index.