Applying the Inverse Square Law

The way that the strength of light gets weaker with distance from the light source is described by the inverse square law. It states that the light intensity gets inversely weaker based on the square of the distance the viewer is away from the light source. Mathematically, we represent it like this:

Just how quickly the light strength falls off with distance will depend on the medium through which the light is traveling. We can calculate the strength of light at a certain distance in the same medium if we know its strength for a previously measured distance. For example, if the light intensity is 10 at a distance of 100 meters from the source, we can calculate the strength that this same light will be at 125 meters, using proportions like this:

This answer makes sense if we think about it as the same light at a further distance being less bright.

The strength of the light being emitted from the light source, as we discussed...