Wavelength: lambda: the distance between any point on a wave and the corresponding point on the next crest (trough) of the wave; distance the wave travels during one cycle; expressed in meters, nanometers, micrometers, picometers m) or angstroms
Here is an excellent lab/exercise to do with middle school kids and older. As metal is heated, electrons are excited and emit different colors (wavelengths) of light (energy) as they bounce between different energy levels.
This 10 question worksheet with answer key allows a way for students to follow along with the Bill Nye Light and Color video. The items are all fill-in-the-blank. The video and worksheet cover the following concepts: white light, primary colors, wavelengths, absorbing/reflecting color, pigments.