RAY THEORY ANALYSIS OF THE SHADOW BLISTER EFFECT

When an extended light source such as the Sun illuminates two objects so that their shadows lie close to each other, the shadow of one of th e objects occasionally appears to bulge out toward the shadow of the o ther. This effect is caused by the overlap of the penumbras of the sha dows and is analyzed here with ray theory. A laboratory demonstration of this phenomenon is performed and compared with theoretical predicti ons. (C) 1998 Optical Society of America.