Question

A light is entering from one medium refractive index `("RI" =5/3)` to another medium at an angle 30°. The angle of refraction for other medium is sin^-1 `(5/6)`. then the increase in angle of incidence is ______ such that the ray of light reflected back into the same medium.

Options

• 5

• 6

• 7

• 8

Answer 1

A light is entering from one medium refractive index `("RI" =5/3)` to another medium at an angle 30°. The angle of refraction for other medium is sin^-1 `(5/6)`. then the increase in angle of incidence is 7 such that the ray of light reflected back into the same medium.

Explanation:

As per Snell's rule,

sin (i)/sin(r) = n₂/n₁

here i = 30°

r = sin^-1 (5/6)

sin r = 5/6

n₂ = ?

n₁ = 5/3

`5/3` sin 30° = n₂

`5/6` ⇒ n₂ = 1

sin(r) = `3/5` ⇒ r = 37°

So, required difference in angle of incidence be 37° – 30° = 7