Optical Disc

A 500 mm dia. disc, marked every 5°, is mounted on a heavy stand and is rotatable around its center. It can be held in any desired position. The lamp house, with a 12V 24 W special filament lamp has rotatable slots to provide light beams of varying widths and also narrow single, double, and triple beams. Attached to the lamp house is an adjustable lens carrier with the lens to provide diverging, parallel or converging light beams that are clearly visible in the classroom. The lamp house 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, a 20 mm thick acrylic semi-circular block, biconvex lens, bi-concave lens each 140mm long and a trapezium with a 125 mm base are provided. Each of these elements has embedded magnets to hold onto the disc.