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 ______.

Options

• `(2sqrt3)/"a"+2"b"`

• `2"a"+(2"b")/3`

• 2a + 2b

• `2"a"+(2"b")/sqrt3`

Answer 1

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 + 2b.

Explanation:

From Snell's law

sin 60° = m sin 30°

⇒ μ = `sqrt3`

Optical path = AO + μ(OB)

= `"a"/cos60^circ  +sqrt3"b"/cos30^circ`

= 2a + 2b