Inverse-square law
In the far field, doubling the distance quarters the power density: the cheapest and most reliable mitigation available.
physics
Last verified 12 August 2026.
- Category
- physics
Definition
Power density from a point source falls as 1/d². Three times the distance is nine times less; ten times the distance is a hundred times less. This is why moving a router across a room outperforms most shielding purchases. Two caveats: it does not apply in the near field, and it does not apply to fields from extended sources such as a long transmission line, where fall-off is closer to 1/d.
Sources
- itu-fs-relations Free-space path loss and power density relations (ITU-R P.525) — International Telecommunication Union. standard, link checked 2026-08-12.
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