Comprises a wooden board painted white, mounted on non-skid plastic feet, and a removable turntable about 170mm in diameter with two orthogonal lines along its diameter dividing it into four equal quadrants. Just beyond the rim of turntable, a circular scale graduated 90o-0-90-0-90 x 10 printed. Also includes a Ray Box with a 12V, 24W bulb. Supplied complete with a cylindrical convex lens of focal length about 75mm and two double slits, giving one wide beam slit and one each of single, triple and five slits.