An unpolarised light of intensity $$I$$ is passed through two polaroids kept one after the other with their planes parallel to each other. The intensity of light emerging from second polaroid is $$\frac{I}{4}$$. The angle between the pass axes of the polaroids is

In the Young's double slit experiment, the intensity of light passing through each of the two double slits is $$2 \times 10^{-2} \mathrm{~Wm}^{-2}$$. The screen-slit distance is very large in comparison with slit-slit distance. The fringe width is $$\beta$$. The distance between the central maximum and a point $$P$$ on the screen is $$x=\frac{\beta}{3}$$. Then, the total light intensity at the point is

For light diverging from a finite point source,

The fringe width for red colour as compared to that for violet colour is approximately