A parallel beam of light of wave length 500 nm in incident normally on a single slit of width $10^{-6}m$. The light is focused by a convex lens on a screen placed in focal plane. What is the angle of diffraction for the first minimum formed?

30°

Angle of diffraction for the first minimum is $\theta = sin^{-1}\frac{\lambda}{a} = sin^{-1}\frac{500nm}{1000nm} = sin^{-1}\frac{1}{2}= 30^o$

The correct answer is Option (2) → 30°