Question

The speed of light will be minimum while passing through
A. Glass
B. Air
C. Water
D. Vacuum

Answer 1

Hint:In order to solve this question, we should know about rarer and denser mediums. Generally, a medium in which speed of light is maximum is known as optically rarer medium whereas the mediums in which speed of light is minimum those mediums are known as optically denser medium. Here, we will discuss each option one by one and later decide which medium light will pass with minimum speed.

Complete answer:
Considering option (A): It’s found that Glass is much denser medium as the refractive index of pure glass lies in between $1.60-1.62$.
Option (B): It’s found that Air is optically a very rarer medium as the value of refractive index of air is generally found as $1.0003$.
Option (c): Water is optically denser medium as compared to that of air but rarer than glass as refractive index of water generally is $1.33$.
Option (D): Since, light travels fastest in vacuum so refractive index of vacuum is $1$
So, among the four options, the denser medium is glass having a refractive index of $1.60-1.62$ so light will travel with minimum speed in glass.

Hence, the correct option is A.

Note:It should be remembered that, Refractive index of a medium is the ratio of speed of light in vacuum and to the speed of light in medium written as $\mu ={\displaystyle \frac{c}{v}}$ as the refractive index of a medium increases the value of speed of light decreases and the speed of light in vacuum is $3\times {10}^{8}m{s}^{-1}$ which is maximum and it’s the universal speed limit.