What is the shape of the wavefront on earth for sunlight?
 

Consider a two slit interference arrangements such that the distance of the screen from the slits is half the distance between the slits. Obtain the value of $D$ in terms of $\lambda$ such that the first minima on the screen falls at a distance $D$ from the centre $O$.

Figure shows a two slit arrangement with a source which emits unpolarized light. $\mathrm{P}$ is a polariser with axis whose direction is not given. If $I_0$ is the intensity of the principal maxima when no polariser is present, calculate in the present case, the intensity of the principal maxima as well as of the first minima.

A small transparent slab containing material of $\mathrm{\mu } =1.5$ is placed along ${\mathrm{AS}}_2$. What will be the distance from $O$ of the principal maxima and of the first minima on either side of the principal maxima obtained in the absence of the glass slab.