A higher transmission voltage is desired to lower energy loss through heating of the transmission wires. Recall that Ohm's law says that energy loss is equal to current times resistance. Rapid alternation of a magnetic field produces an electric field. If a wire is in that electric field, current will flow. Rapid alternation of an electric field produces a magnetic field.
Light makes up a relatively small portion of the electromagnetic spectrum.
The two components of an electromagnetic wave are its electric component and its magnetic component. The frequency of the vibrating electron that produces light is the same as the frequency of the light produced. Radio waves have longer wavelength than light, which has a longer wavelength than X-rays.