Question

In a Young’s double slit experiment, bichromatic light of wavelengths 400 nm and 560 nm are used. The distance between the slits is 0.1 mm and the distance between the slits and screen is 1 m. The minimum distance between two minima is

(a)  4 mm 

(b)  5.6 mm 

(c)  14 mm

(d)  28 mm 

Answer 1

Correct option  (d) 28 mm 

Explanation:

The condition for minima (dark fringes) is

The possible values are n₁ = 3, m₁ = 2;  n₂ = 10, m₂ = 7 and so on. Area where the minima of both wavelengths coincides is the area of total darkness. The width of this area is