This module simulates the behavior of light as it passes through lenses and stops on an optical "bench". The user can use either a two-dimensional object (five point sources in the shape of a T), or a three-dimensional object (a large number of point sources on the surface of a tea pot or a banana). The user can put up to three lenses and two stops on the bench. The position, diameter, and focal length of each lens can be varied interactively, as can the position and diameter of each stop. Each point source on the object emits a large number of rays at random angles, forming a cone-shaped distribution that covers the area of the first optical element. These rays travel through the system according to the laws of geometrical optics, and a ray is discarded if it misses an optical element. A movable observation screen allows the user to see the ray distribution in any plane perpendicular to the axis of the optical "bench".