A parallel beam of monochromatic light of wave-length 450 nm passes through a slit of width 0.2 mm. Find the angular divergence in which most of the light is diffracted

Most of the light is diffracted between the two first order minima. These mimima occur at angle given by dsinθ=±nλFor n=1,   sinθ=±λd=±450×10−90.2×10−3=±2.25×10−3 rad∴The angular divergence=2×θ = 2×2.25×10−3rad                                                                                             = 4.5×10−3rad