VHF (very high frequency) television antennas in England are oriented vertically, but those in North America are horizontal. The difference is due to the direction of oscillation of the electromagnetic waves carrying the TV signal. In England, the transmitting equipment is designed to produce waves that are polarized vertically;that is, their electric field oscillates vertically. Thus, for the electric field of the incident television waves to drive a current along an antenna (and provide a signal to a television set), the antenna must be vertical. In North America, the waves are
polarized horizontal Figure 34-IOa shows an electromagnetic wave with its electric field oscillating parallel to the vertical y axis. The plane containing the l vectors is called the plane of oscillation of the wave (hence, the wave is said to be plane-polarized in the y direction). We can represent the wave’s polarization (state of being polarized) by showing the directions of the electric field oscillations in a “head-on” view of the plane of oscillation, as in Fig. 34-IOb. The vertical “double arrow” in that figure indicates that as the wave travels past us, its electric field oscillates vertically-it
continuously changes between being directed up and down along the y axis.