devarshi-dt-logo

Question:

A ray of light AO in vacuum is incident on a glass slab at angle 60° and refracted at angle 30° along OB as shown in the figure. The optical path length of light ray from A to B is :

2a+2b3`

23a+2b

2a+2b3

2a+2b

Solution:

Correct option is A. 2a+2b
From Snell's law
1.sin60° = μsin30° ⇒ μ = √3
Optical path = AO + μ(OB) = acos60° + √3bcos30° = a/2 + √3b(√3/2) = a/2 + 3b/2 = (a+3b)/2