The Inverse Square Law is a principle in physics that deals with forces that spread in all directions equally. These forces include sound, light and gravity. The law describes how the strength of these forces weaken over increased distances.
This law relates to the hobby of fluorescent mineral collecting, when trying to determine the wattage needed for an ultraviolet lamp, based on the distance that the lamp will be from the mineral specimens on display.
For instance, the law states that the intensity (I) of the electromagnetic energy (ultraviolet light) hitting a fluorescent mineral specimen, is inversely proportional to the distance (d) from the energy source (ultraviolet lamp).