The intensity at the central maxima `(O)` in a Young's double slit experiment is `I_0` . If the distance OP equals one-third of fringe width of the pattern, then show that the intensity at point P would be `I_0

Question

The intensity at the central maxima `(O)` in a Young's double slit experiment is `I_0` . If the distance OP equals one-third of fringe width of the pattern, then show that the intensity at point P would be `I_0 //4`.