[UPSC CSE 2013] Diffraction (Q254, 15M)

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 \begin{qroman}\item first two minima and \item first two maxima on the screen.\end{qroman}