Demo 21-11 Radio Waves

A radio wave system with a wavelength of about 3 meters is used to illustrate the existence and transmission of radio waves. A dipole transmitting antenna is oriented horizontally. A dipole receiving antenna indicates the reception of radio waves by an incandescent lamp whose intensity increases with the strength of the wave. When the receiving antenna is held close to and parallel to the transmitting antenna, the light glows brightly, as shown in Figure 1. As the receiver is moved further from the transmitter, the light becomes dimmer. When the two antennas are oriented perpendicular to each other, the light goes out, indicating the polarization of the radio waves