This self-contained unit allows students to measure and study light refraction. The angle of incident and refractive rays are readily seen with the help of a built-in laser as its light source. Add water up to the tank’s midline to create a surface that precisely transmits and reflects the laser beam for student observations. The laser revolves around the circular graduated scale and can be set at any point. Students can observe light rays as they travel from air into water, water into air, and water into water. Detach the apparatus from the tank to perform refraction and reflection experiments with the included prisms and mirrors. Includes: 4 prisms, 2 mirrors, laser, instructions and a Teacher's Guide.