Teaching Notes

The geometry of the shadows can be challenging. It may help to point a meter stick from a light to the puppet and to ask where that light will reach the screen. Also, with all three lights on, you can ask the students what will happen if you block the lights one at a time (for example, by covering one with a book or clipboard). Encourage the students to compare their observations for the colors they observe with their expectations. You might ask how the unexpected colors might become part of the student’s light show.

If you have only one set of colored lights, at any given time you will have to keep the students busy and productive on other parts of the activity. If you have prisms available, you might have each group do a simple prism activity at this time.

Safety Precaution: Be extremely careful with 110-V bulbs. Explain to the students that they must not touch the bulbs.

Most students have little experience with combining colored lights. They probably will be surprised that red light plus green light looks yellow. It may help to explain that what is complicated here is not the physics but rather the functioning of the eye and brain. In fact, the way we commonly refer to light as “red” or “green” may create the preconception that the color is somehow embedded in the light, rather than being a sensory response to the physical characteristic of wavelength.