Define Snell's law of refraction. A ray of light is incident on a glass slab at an angle of incidence of 60°. If the angle of refraction be 32.7°, calculate the refractive index of glass. (Given : sin 60° = 0.866, and sin 32.7° = 0.540).

According to Snell’s law, the ratio of sine of angle of incidence to the sine of angle of refraction is equal to the constant for a given pair of media.

$Refractive\ index=\frac {sine\ of\ angle\ of\ incidence}{sine\ of\ angle\ of\ refraction}$ or $\frac {sin\ i}{sin\ r}=n\ (constant)$

Given:

Angle of incidence, $\angle i$ = 60°

Angle of refraction, $\angle r$ = 32.4°

To find: Refractive index, $n$   

Solution:

From the refractive index formula, we have- 

$n=\frac {sin\ i}{sin\ r}$

Substituting the given values in the formula we get-

$n=\frac{sin\ 60^º}{sin\ 32.7^º}$

$n=\frac{0.866}{0.540}$

$n=1.60$

Thus, the refractive index of glass is 1.60.

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Updated on: 10-Oct-2022

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