The refractive index of crown glass is close to 3/2. If the speed of l

The refractive index of crown glass is close to 3/2. If the speed of light in air is c, then the speed of light in the crown glass will be close to

(3/2)c
(4/9)c
(2/3)c
(9/4)c
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UPSC NDA-2 – 2022
The refractive index (n) of a medium is defined as the ratio of the speed of light in a vacuum (or approximately in air) to the speed of light in that medium (v). The formula is n = c / v, where c is the speed of light in vacuum/air.
Given that the refractive index of crown glass is close to 3/2, we have n = 3/2.
Using the formula n = c / v, we can rearrange it to solve for the speed of light in the glass (v): v = c / n.
Substituting the given refractive index: v = c / (3/2).
To divide by a fraction, we multiply by its reciprocal: v = c * (2/3) = (2/3)c.
The refractive index indicates how much the speed of light is reduced when it passes through a medium compared to its speed in a vacuum. A higher refractive index means a lower speed of light in the medium.
The speed of light is highest in a vacuum (approximately 3 x 10⁸ m/s) and slows down when it enters any medium, causing light to bend (refract). The refractive index is a dimensionless quantity.