ArtLex
Art Lex: Composition
This online dictionary of art terms from Artlex is a valuable tool. The composition page explains how the term is used in the world of art. There are related links and works of art to explore.
Exploratorium
Exploratorium: Water Sphere Lens
A discussion of how to make a magnifying lens exhibit using a water-filled flask and a light bulb. Consists of assembly instructions and a "To do and notice" section. Great for a teacher demonstration or a student project.
Ducksters
Ducksters: Physics for Kids: Lenses and Light
Kids learn about lenses and light in the science of physics including concave, convex, converging, diverging, focal point, meniscus, and Plano lenses.