Researchers use different wavelengths to reveal features not visible in white light.
"Do you see what I see?": A lesson about the astronomical imaging, how to build a color wheel, and online activities seeing the Crab Nebula at different wavelengths.
"Star Light, Star Bright" activity has good background information on waves and excellent electromagnetic spectrum diagram.
Explains the electromagnetic spectrum through puzzles and question and answer format in easy to understand terms.
Excellent background information on the electromagnetic spectrum with links to activities and a quiz on the electromagnetic spectrum.
NASA's Infrared Processing and Analysis Center's Infrared Astronomy: a terrific site providing background information on infrared astronomy from the days of Herschel to the present. Great infrared images!
Great graphic on the electromagnetic spectrum, and interesting at home experiment on infrared radiation using a TV remote.