Study image formation with lenses. The screen view shows the pattern of illumination on the screen, regardless of its location. Also, the eye view shows what the eye sees without the screen. (The eye has a "near point," so if it gets too close, the image blurs).

General palette with tools to draw single light rays and sprays of light rays, point sources, line and complex sources, screen, eye, blocker and lens (converging or diverging).

Measurement palette to measure distances, angles and light intensity.

Graphics palette, including snapshot tool