He–Ne laser — UPSC CSE 2013 Physics PYQ

A parallel beam of light from a He–Ne laser (\lambda=630 nm) is made to fall on a narrow slit of width 0.2\times10^{-3} m. The Fraunhofer diffraction pattern is observed on a screen placed in the focal plane of a convex lens of focal length 0.3 m. Calculate the distance between the

(i) first two minima and

(ii) first two maxima on the screen.