Light

"light carries energy
brighter light carries more energy
forms of light can be either visible or invisible
natural and artificial light have measurable properties (e.g., colour, wavelength, brightness)
light can travel in a straight path (rays) light rays change direction (bend, refract) as they pass from one medium to another"
vocabulary: reflect, refract, absorb, transmit, natural, artificial, light beam, transparent, translucent, opaque, spectrum
sources: Mission Hill Elementary School
How we see things interactive from BBC
The World of Science (children's reference book) from Parragon (section 4, page 109)
"The Amber Spyglass: How to see invisible light and the way scientists work" in The Science of Philip Pullman's His Dark Materials (part of this chapter is available through Google Books)