PURPOSE: To show that light obeys the Inverse Square Law.
DESCRIPTION: A poster of four equal squares is placed against the wall and a light source is positioned in the middle of the room. The room lights are turned off so that the light from the light source illuminates thge poaster. A hand held square is held up to the poster and is seen to be one quarter square. When the square is placed one half the distance to the light source the shadow si sen to be four times greater.
EQUIPMENT: Poster, light, square.
Updated by Jun Qi in 3/22/2000