Aerial (antenna)

When an alternating current drives a transmitting aerial, charges in the aerial accelerate back and forth. Their changing distribution produces changing electric and magnetic fields. These changing fields travel away from the aerial as an electromagnetic wave.

If an electrical circuit supplies a rapidly alternating current to a transmitting aerial, electric charges move back and forth in the aerial. This oscillation produces a radio wave that travels away through space. The wave has the same frequency as the oscillation producing it: if the charges complete more back-and-forth cycles each second, the radio wave has a higher frequency.