Question

Young's double slit experiment is made in a liquid. The 10^th bright fringe lies in liquid where 6^th dark fringe lies in vacuum. The refractive index of the liquid is approximately

Options

• 1.8

• 1.5

• 1.3

• 1.6

Answer 1

1.8

Explanation:

Fringe width ω = `(λ"D")/"d"`

When the apparatus is immersed in a liquid, then λ will decrease µ times and hence ω is reduced µ (refractive index) times.

10ω' = (5.5)ω

or `10λ"'"("D"/"d") = (5.5)(λ"D")/"d"`

or `λ/(λ"'") = 10/5.5` = µ

or µ = 1.8