Alight ray in water is incident on a boundary with air at an angle of 22°. the refractive index of water is 1.33 and that of air is 1.00. what is the angle of refraction in air?
a) 15°
b) 22°
c) 30°
d) 45°

C) 30°  

Explanation:

According to laws of refraction:

1. The incident ray, the normal and refracted ray- all lie in same plane.

2. The angle of incidence (i) and angle of refraction (r) are related as:

η₁ sin i = η₂ sin r (Snell's Law)

where η₁ is the refractive index of the medium in which incident ray lies and η₂  is the refractive index of the medium in which refracted ray lies.

Given:

η₁ = 1.33 (water)

η₂ = 1.00 (air)

i = 22°

r = ?

⇒1.33 sin 22° = 1.00 sin r

⇒ r = sin⁻¹ (0.50) = 30°

Thus, the angle of refraction is air is 30°