Looking at the double slit pattern produced by a laser of wavelength 532 nm, you notice that the 7th maximum of interference is not present. It falls on the first minimum of diffraction (due to the slits width). Moreover, you notice that the last bright fringe of interference (2-slit interference) you see is for m=21 (at the largest possible angle). If d is the slit separation, and a is the slit width:
Find the ratio r = d/a
