Question

In Young's double slit experiment, the slits S₁ and S₂ are 3 mm apart and the screen is placed 1.0 m away from the slits. It is observed that the fourth bright fringe is at a distance of 5 mm from the second dark fringe. Find the wavelength of light used.

Answer 1

Given: d = 3 mm = 3 × 10⁻³ m, D = 1.0 m

According to the question,

`(5beta)/2 = 5 xx 10^-3`

⇒ `5/2 xx (lambdaD)/d = 5 xx 10^-3`

⇒ `lambda = (2d xx 10^-3)/D`

 = `(2 xx 3 xx 10^-3 xx 10^-3)/1`

⇒ λ = 6 × 10⁻⁶ m