The Inverse Square Law applies to several areas of the AV industry, including working with a sound system, predicting the brightness of images projected onto a screen, and event lighting. You are more familiar with this law than you might think. You know that when you move closer to a source of sound, it seems louder. Similarly, the closer you get to a source of light, such as a flashlight, the brighter it seems. The Inverse Square Law explains these changes in perceived loudness and brightness.

LO glossary element icon
Glossary
Inverse Square Law

The inverse square law states that the physical quantity or strength is inversely proportional to the square of the distance from the source of that physical quantity. This means that as the distance from a point source of energy (light or sound) doubles, the energy will be distributed over four times the area. The resulting energy will be one-fourth the original intensity.