Inverse Square Law

Newtons Inverse Square Law

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).

Below is a diagram which helps to illustrate the inverse square law, and how it affects the intensity of ultraviolet light used for the fluorescent mineral hobby. As you can see from the diagram below, as you double the distance that the specimen is from the ultraviolet lamp, the intensity of ultraviolet light hitting the specimen is reduced to 1/4. If you triple the distance, the intensity of ultraviolet light is reduced to 1/9 etc.

Now by visualizing the diagram above, you can see how a 9-watt ultraviolet lamp may be sufficient enough for a specimen to fluoresce at a distance of 1 foot, but at a distance of 2 or 3 feet, the lamp no longer can provide enough energy for the specimens to respond adequately. This problem is resolved by investing in larger, more powerful ultraviolet lamps.

For this reason Polman Minerals recommends that you consult with us about what lamp is best suited for your individual needs. If you are planning to build a display case for your fluorescent mineral specimens, Polman Minerals will be happy to discuss the optimal size for your case, as well as the appropriate wattage for your lamp(s).