A 500 mm diam. disc marked every 5° is mounted on a heavy stand and is rotatable around its centre. It can be held in any desired position. The lamphouse, with a 12V 24 W special filament lamp has rotatable slots to provide light beams of varying widths & also narrow single, double & triple beams. Attached to the lamp house is an adjustable lens carrier with lens to provide diverging, parallel or converging light beams which are clearly visible in classroom. The lamphouse can be held in any desired position around the disc.
Optical elements are two 50 x 25 mm plane glass mirrors, and a metallic cylindrical mirror, each mounted in a holder, for reflection. For refraction, 20 mm thick acrylic semi-circular block, bi-convex lens, bi-concave lens each 140 mm long & a trapezium with 125 mm base are provided. Each of these elements has embedded magnets to hold on to the disc.