In Young’s double slit experiment, the slits are 2 mm apart and are illuminated with a mixture of two wavelength λ = 750 nm and λ = 900 nm.

Question

In Young’s double slit experiment, the slits are 2 mm apart and are illuminated with a mixture of two wavelength λ₀ = 750 nm and λ = 900 nm. What is the minimum distance from the common central bright fringe on a screen 2 m from the slits where a bright fringe from one interference pattern coincides with a bright fringe from the other?

Answer 1

Now from the question we can infer that 

D = 2; d = 2

n₁λ₁ = n₂ λ₂

5^th and 6^th fringes will coincide respectively. The minimum distance is given as

= 4500 x 10^-6 = 4.5 x 10^-3 m 

X_min = 4.5 mm