Question

In a Young's double slit experiment, a laser light of 560 nm produces an interference pattern with consecutive bright fringes separation of 7.2 mm. Now another light is used to produce an interference pattern with consecutive bright fringes separation of 8.1 mm. The wavelength of second light is ______ nm.

Options

• 530

• 230

• 430

• 630

Answer 1

In a Young's double slit experiment, a laser light of 560 nm produces an interference pattern with consecutive bright fringes separation of 7.2 mm. Now another light is used to produce an interference pattern with consecutive bright fringes separation of 8.1 mm. The wavelength of second light is 630 nm.

Explanation:

Fringe width, β = `"D"/"d"`λ   ∴ β ∝ λ  

∴  λ₂ = `8.1/7.2` λ₁ = `9/8` λ₁

∴ wavelength of second light, λ₂ = `9/8`

λ₁ = `9/8xx560`

= 630 nm