A light ray travelling in glass medium is incident on glass-air interface at an angle of incidence $$\theta$$. The reflected (R) and transmitted (T) intensities, both as function of $$\theta$$, are plotted. The correct sketch is

A long insulated copper wire is closely wound as a spiral of N turns. The spiral has inner radius a and outer radius b. The spiral lies in the xy-plane and a steady current I flows through the wire. The z-component of the magnetic field at the centre of the spiral is