In a double slit experiment suppose that light emerging from the slits is intense enough to reach far off distances on the screen. Usually, the fringe width is expressed as  $\frac{\lambda D}{d},$ where the symbols have their usual meanings; but this is true only if  $y<<D,$ where $y$ is the distance on the screen from the central bright fringe to the point of observation. If the fringe width is  $p\lambda D/d$  at an angular position, $\theta =\frac{\pi }{3}$ relative to the central axis. Then find $p$. (Note that here $y$ is comparable to  $D$).