Question

In double-slit experiment using light of wavelength 600 nm, the angular width of a fringe formed on a distant screen is 0.1°. What is the spacing between the two slits?

Answer 1

The wavelength of the light is, λ=600 nm.

Angular width of the fringe in the air is, θ 1 =0.1°.

Convert the width into radian,

θ 1 =0.1× π 180 = π 1800  rad

The relation of slit spacing ( d ) with the angular width is,

d= λ θ = 600× 10 −9 3.14 1800 = 108× 10 −5 3.14 =3.44× 10 −4  m

Thus, the spacing between the slits is 3.44× 10 −4  m.