The study of how EM waves travel and interact with matter can become
extremely complex. However, there are several important simplifications that
can be made to more easily study the properties of EM waves. Historically,
these simplifications were developed for light waves, but they also apply to
radio waves, microwaves, and the entire EM spectrum.
In a vacuum, 2.4 GHz microwaves travel at the speed of light. Once started,
these microwaves will continue in the direction they were emitted forever,
unless they interact with some form of matter. The geometric ray is used to
signify that the microwaves are traveling in free space. Since WLANs are
usually on earth, within the atmosphere, the microwaves are traveling in air,
not in a vacuum. However, in the next section the student will see that this
does not significantly change their speed.
Similar to light, when RF
travels through transparent matter, some of the waves are altered. Therefore,
the velocity of 2.4 GHz and 5 GHz microwaves also changes, as the waves travel
through matter. However, the amount of alteration depends heavily on the
frequency of the waves and the matter. In the next two sections, some of the
phenomena that can affect WLAN radio waves as they travel through matter will
be studied.