The Apparent Brightness (B) of a source is inversely proportional to the square of its distance (d): Implications: For a light source of a given Luminosity... It will appear 22=4 times brighter.
Every light source is different, but the intensity changes in the same way. The intensity of light is inversely proportional to the square of the distance. This means that as the distance from a light source increases, the intensity of light is equal to a value multiplied by 1/d2
This relates the Apparent Brightness of a star (or other light source) to its Luminosity (Intrinsic Brightness) through the Inverse Square Law of Brightness: At a particular Luminosity, the more distant an object is, the fainter its apparent brightness becomes as the square of the distance
