Use this self-contained unit to measure and study the refraction of light. Incident and refractive rays are easily seen and measured by using this product. Refraction of light can be studied with the help of a built-in laser as a light source which revolves and can be fixed at any point around a circular graduated scale. The unit is made with leveling screws to level the water in the tank. Unit measures 6.75" x 5.5" x 10" and holds 400mL of water. Includes LR44 battery, Teacher's Guide and student handout.