CCNA Wireless 640-722 Official Cert Guide

Diffraction

Suppose an RF signal approaches an opaque object, or one that is able to absorb the energy that strikes it. You might think that the object would produce a shadow in place of the signal that is absorbed, much like an object might make a shadow as light shines on it. If a shadow formed, it might make a dead or silent zone in the RF signal behind the object.

With RF propagation, however, the signal tends to bend around the object and eventually rejoin to complete the wave. Figure 3-13 shows how a radio opaque object can cause diffraction of an RF signal. Diffraction is best viewed as concentric waves, rather than an oscillating signal, so that its effect on the actual waves can be seen. In the figure, diffraction has caused the signal ...