Demonstrate the principles of reflection and refraction with this affordable optical block set. The set includes 3 well-made glass blocks in 3 shapes: trapezoidal, semicircular, and double convex. When light passes through the trapezoidal block, it is refracted at each boundary between glass and air. Both refraction and reflection can easily be seen using the semicircular block. Shine three light rays through the convex lens to show how they converge at the focal point and then calculate focal length. Purchase one for classroom demonstration or multiple sets for students to study in groups!