Question

A Slit of width 12 × 10^–7 m is illuminated by light of wavelength 6000 Å . The angular width of the central maxima is approximately ______ . 

(A) 30° (B) 60° (C) 90° (D) 0°

Answer 1

The correct option is  (B) 60°.

Explanation:

If θ is angular position of first minimum then

sin θ = (λ/a)

here   λ = 6000 Å  &  a = 12 × 10^–7 m

 sin θ = 500 × 10^–3

 θ = sin^–1(0.5) = 30°

angular width of central maximum = W_θ = 2θ = 2 × 30° = 60°.