There always seems to be two camps when it comes to photography: those who go by feel and those who go by technique. Neither one is necessarily a wrong approach but knowing the technical stuff definitely helps when you are faced with problems or unexpected results. In this video Mark Wallace explains the inverse square law and how it affects light falloff. I'll admit, not having gone to school for photography, it did take me a while to completely grasp this idea when I first started shooting. Once you understand this concept, you should be able to not only light your scenes better but also become more versatile when giving a single light double duty lighting both your subject and the background.