Curated OER
Modular Mathematics
Students are introduced to modular mathematics. They start by making clocks for different bases. They use their clocks to count, using the base, and then finding the mod or remainder. They explore both positive and negative numbers with...
University of Colorado
University of Colorado: Physics 2000: Quantum Atom
Several pages with an interesting discussion of the visible light spectrum and atomic absorption and emission line spectrum. Features excellent graphics, thorough and understandable discussion, and many interactive Java applets.
Exploratorium
Exploratorium: Online Exhibit: Mix and Match
A Shockwave movie which allows users to mix varying colors of light and observe the effect upon the appearance of a circle. Accompanied by a "To Do and Notice" section and a "What's Going On?" section. Excellent!