law of inverse square

(physics) Any law in which a physical quantity varies with distance from a source inversely as the square of that distance.

Any law in which a physical quantity varies with distance from a source inversely as the square of that distance. When energy is being radiated by a point source (see illustration), such a law holds, provided the space between source and receiver is filled with a nondissipative, homogeneous, isotropic, unbounded medium.

Point source S emitting energy of intensity I. The inverse-square law states that I₁/I₂ = r₂²/r₁², where r = distance from S.

Similar reasoning shows that the same law applies to mechanical shear waves in elastic media and to compressional sound waves. The term is also used for static field laws such as the law of gravitation and Coulomb's law in electrostatics.

Principle stating that the strength of radiation from a point source varies inversely as the square of the distance.

A law which applies to a light source (or to a sound source) that is in a space far away from any reflecting surface: the intensity at a point, as measured on a surface which is perpendicular to a line drawn between the point and the source, varies inversely with the square of the distance between the point and the source. (For sound waves, this decrease in intensity is equivalent to a drop in sound-pressure level of 6 dB for each doubling of distance from the source.)

inverse-square law

The principle that the intensity of radiation is inversely proportional to the square of the distance from the source of radiation to the irradiated surface.