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Wireless & Mobility · Intermediate

Inverse Square Law

Power density falls in proportion to the square of the distance from the source.

Definition

Because an RF wavefront expands spherically, the power density at any point decreases with the square of distance. This principle underlies free space path loss calculations. Doubling distance cuts power density to one quarter, which is a 6 dB loss.

Exam tip

Inverse square law explains the 6 dB rule used in link budget questions.

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