Plane polarised light is passed through a polaroid. On viewing through the polaroid we find that when the polariod is given one complete rotation about the direction of the light, one of the following is observed

The intensity of light gradually decreases to zero and remains at zero

For single slit diffraction pattern $d \sin \theta=\lambda$ (d= slit width)

Angular width = $2 \theta=2 \sin ^{-1}\left(\frac{\lambda}{d}\right)$

It is independent of D i.e. distance between screen and slit