Walter Fendt
Walter Fendt: Reflection and Refraction of Light
Defines the refraction of light and provides an applet for investigating it.
Georgia State University
Georgia State University: Hyper Physics: Lens Maker's Formula
A discussion of the lens-maker's formula and its use in determining the effect of lens shape and index of refraction upon the magnifying power of a lens. Includes an interactive problem-solving section.
Optical Society
Optical Society of America: Optics for Kids: Total Internal Reflection
An investigation into the total internal reflection of light, using a laser pointer. Accompanied by an explanation of what's happening, a discussion of Snell's Law, and links to additional information.