A beam of light of λ=600nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between first dark fringes on either side of the central bright fringe is

Here, λ=600nm=600×10-9 ma=1 mm=10-3 m,D=2 mDistance between the first dark fringes on either side of the central bright fringe is also the width of central maximum.  Width of central maximum =2λDa=2×600×10-9 m×2 m10-3 m=24×10-4 m=2.4×10-3 m=2.4 mm