Question

A single slit of width a is illuminated by a monochromatic light of wavelength 600 nm. The value of ‘a’ for which first minimum appears at θ = 30° on the screen will be

(1) 0.6 μm

(2) 1.2 μm

(3) 1.8 μm

(4) 3 μm

Answer 1

(2) 1.2 μm

As for first minima

a sinθ = λ