I almost understand how the inverse square law is derived from the area of sphere equation, 4πr2, but I'm not quite clear on what happens to the 4π. I found one equation that seemed to say that the intensity is equal to the area of the sphere of the source point times the amount of whatever coming from that source point, divided by the area of the sphere at the distance one is interested in. So that way the 4π cancels out since it's common to the numerator and denominator. Is that right? If so, does that mean that the radius of the source point is always assumed to be 1?