Great for elementary and middle school as an intro to new material. Light is a mysterious thing, but that doesn't mean that we can't learn about it while we ride up the crests of a wave and back down through the troughs. This article also explains how to brag to your friend about how extreme a hill is with amplitude and how far you traveled by measuring the wavelength of the light wave.
Vocab words: trough, crest, amplitude, wavelength
Check out 300+ articles just like this, written at 7 reading levels here