We have seen so far that when an electromagnetic disturbance exists in space (for example, as the result of a point source of electromagnetic oscillations), this disturbance will be propagated in many directions. There are, however, some directions in which no radiation will be found, even if the medium is isotropic and homogeneous. The energy, which was originally concentrated in a small volume, will spread itself over an increasingly wide space. The field strength will thus become steadily less as the distance from the source increases.
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