Q.
A beam of light of λ=600nm from a distant source falls on a single slit 1mm wide and the resulting diffraction pattern is observed on a screen 2m away. The distance between first dark fringes on either side of the central bright fringe is
Here, λ=600nm=600×10−9m a=1mm=10−3m,D=2m
Distance between the first dark fringes on either side of the central bright fringe is also the width of central maximum.
Width of central maximum =a2λD =10−3m2×600×10−9m×2m =24×10−4m =2.4×10−3m =2.4mm