This well-written explanation of relativity includes animations and pictures which may be helpful in understanding a tough topic.

A discussion of refraction and its application to sound waves. Using analogies, graphics and real-life applications, this page and those that accompany it explain why and when sound waves bend.

This page defines electromagnetic radiation. Included are links to more information.

[Free Registration/Login Required] Students draw conclusions and engage in tables and charts involving cumulative frequency; a wonderful review of student's knowledge.