Physics Classroom
The Physics Classroom: Refraction and Ray Model of Light: The Critical Angle
Illustrated examples and interactive practice problems that introduce students to the concept of the critical angle, the angle of incidence that provides an angle of refraction of 90-degrees.
Exploratorium
Exploratorium: Critical Angle
Students can see light reflected and refracted in this demonstration. They will also discover the total internal reflection of light.
Georgia State University
Georgia State University: Hyper Physics: Total Internal Reflection
This physics department site provides a definition and explanation of the phenomenon of total internal reflection. Includes a diagram and an equation for calculating the critical angle for light approaching a surface.
Georgia State University
Georgia State University: Hyper Physics: Reflection and Refraction
Reflection and refraction are explained with an experiment that uses a sheet of paper, cardboard, and other common materials.
Boston University
Bu: Optics: Geometric Optics
Several short descriptions of demonstrations which illustrate principles of geometric optics (many of which focus upon refraction).
BBC
Bbc: Gcse Bitesize: Why Do Scientists Think That Light and Sound Are Waves?
Light travels as transverse waves and can travel through a vacuum. Sound travels as longitudinal waves and needs to travel through a solid, liquid or gas. Read about the properties of light and of sound, and learn the differences between...