Metal detector works on the principle of

A copper disc of radius 0.1 m rotates about an axis passing through its centre and perpendicular to its plane with 10 revolutions per second in a uniform transverse magnetic field of 0.1 T . The emf induced across the radius of the disc is

At very high frequencies, the current ( $i$ ) in the given circuit is

Electromagnetic radiation of intensity $0.6 \mathrm{Wm}^{-2}$ is falling on a black surface. The radiation pressure on the surface is