diagram of extinction of light from a source such as an electric light in a reflector, illustrating(i)transmitted, (ii) scattered, and(ii)absorbed light. (b)A diagram of daylight visibility, illustrating (1) residual light from a target reaching an observer, (i)light trom a target scattered out of an observers line of sight, (ii) air light from the intervening atmosphere, and (iv) air light constituting horizon sky