Question: In Young\'s double-slit experiment, if the distance between the slits is 0.2 mm and the distance to the screen is 1 m, what is the fringe width if the wavelength of light used is 500 nm?

Options:

1. 0.1 mm
2. 0.2 mm
3. 0.5 mm
4. 0.8 mm

Correct Answer: 0.1 mm

Solution:

Fringe width (β) = λD/d. Here, D = 1 m, d = 0.2 mm = 0.0002 m, λ = 500 nm = 500 x 10^-9 m. β = (500 x 10^-9 * 1) / 0.0002 = 0.0025 m = 0.25 mm.