The Hollow Acrylic Prism & Stopper, 2 Inch is a physics education tool designed for demonstrations involving refraction. Constructed from acrylic. Hollow prism with stopper used when studying Snell's Law of Refraction. When referring to light or other waves passing through a boundary between two different isotropic media, Snell's law can be used to describe the relationship between the angles of incidence and refraction. Useful when studying other principles of light manipulation, light rays, and light angles.