Which of the following has its permeability less than that of free space?

A square shaped coil of side $$10 \mathrm{~cm}$$, having 100 turns is placed perpendicular to a magnetic field which is increasing at $$1 \mathrm{~T} / \mathrm{s}$$. The induced emf in the coil is

Which one of the following electromagnetic radiation has the least wavelength?

In a Young's double-slit experiment, the screen is moved away from the plane of the slits. What will be its effect on the following?

(i) Angular separation of the fringes.

(ii) Fringe-width.