Specifications: This apparatus is used for the study of the characteristics of light when travelling through a medium. The medium includes concave and convex lens. Light travels through a white background which different sizes of slit. This set includes 2 convex lens, 2 concave lens, 1 triangle, 1 semicircle, and 1 prism, and 2 background mirrors. All of these equipment are attached to a small magnet, in which all of the objects can be placed on a screen. The base under the screen is of size 20x80cm and 15cm in height. There are 3 switched for the operation of 3 light bulbs above the base, in which every spot have a place for inserting the slits. The screen above is of size 45x80cm.