Experiencing Invisible Light
Topic/Concept: Ultraviolet and Infrared Light.
Type of Activity: Small group.
Prerequisite knowledge required: None.
Resources required: An ultraviolet light that is not too bright in the optical (we had a pretty fancy one from (i think) a company called Raytech); Sunscreen; Paper; UV beads; Digital Camera; Remote Controls
Learning Objectives: There is light your eyes can not see. These other kinds of light can be useful (or harmful!) in ways similar to the light we see, although there are some surprises!
Common misconceptions: That IR and UV light are somehow weird, magical, or a strange force of nature. I also hate it when people say IR light is heat. We didn’t really talk about that here, though :)
Detailed description of activity: First, I asked students about the sun. “How does the sun affect you? Do you need the sun? If it went out tomorrow, what would happen to our world?” Then I drew their attention to the fact that the sun emits a lot of different kinds of light that our eyes can not see. One such kind of light is infrared. I held up a remote control, and asked all the kids if they knew what it was. They did. They hypothesized about how it works. I let them all try pointing the remote at the digital camera while we were either taking a movie. If they are pushing a button, another student looking through the camera should be able to see a bright red light. In some remote controls, this pulses. Talk about how your digital camera can see light beyond what your eye can see.
Next, it’s time to play around with ultraviolet light. It’s fun to put sunscreen on one hand, and no sunscreen on the other. The hand with sunscreen reflect much less ultraviolet light. Talk about how the metals in the sunscreen absorb the ultraviolet light before it hits your skin, so that the ultraviolet light can not harm you. You can also make invisible art on paper if you “draw” with sunscreen (a thin layer will do). When you shine the UV light on the paper, the places where you applied the sunscreen should be black. Finally, shine the UV light on the UV beads, and let the kids shine a normal flashlight on some other UV beads. Show them that they change color under the UV light, but not under the normal incandescent light. Give each kid a few beads and make them guess what will happen when they take them out in the sun.
Assessment: On the fly, while interacting with students.
Associated files and images: None.
Comments: This is a ~15 minute activity for elementary/middle school students in an informal outreach setting.