## College Physics (4th Edition)

As the wave propagates away from the antenna, the electric field is oriented in the same direction as the antenna. That is, the electric field is also oriented horizontally north-south. Since the electric field oscillates horizontally as the wave propagates, the magnetic field oscillates vertically as the wave propagates east from the transmitter. To detect the magnetic field of the wave, we need an area $A$ for the changing magnetic field to pass through. As the magnitude of magnetic flux is $A~B~cos~\theta$, ideally we would like the angle between the area and the oscillating magnetic field to be zero. Thus, the magnetic dipole antenna used to detect the magnetic field should be oriented so the area of the receiver faces up and down, so the magnetic field oscillating vertically passes through it with an angle of zero.