When dealing with source originating from a very small point but propagating in all directions, we have a condition of maximum divergence. Such point source have an intensity that decreases as the inverse square of the distance from the point. This can be seen from a consideration of the divergence. Suppose a source delivers a power P of light as shown in Figure 6.5 The intensity at a distance R is found y dividing the total power by the surface area of a sphere of radius R from the source.