Rainbows are an interesting phenomenon to children of all ages, so they make for a good starting point in learning about colors, bending light and wavelengths. Adjust a rainbow unit to fit the needs of your class, whether that's a short afternoon lesson, or several activities spread throughout the month. Your students will have fun while they learn.
Read a book that introduces the concept of a rainbow. In "What Makes a Rainbow?" by Betty Ann Schwartz, a young rabbit asks other animal friends what makes a rainbow, and each replies with a color that's important to him. In "A Rainbow of My Own" by Don Freeman, a young child tries to capture a rainbow. If your students enjoy nonfiction, "All the Colors of the Rainbow" by Allan Fowler explains where rainbows come from. After reading, ask children if they've seen a rainbow, and where those rainbows might show up. For example, aside from a rainbow in the sky, they might have also seen rainbows in bubbles or in an oil spill in the driveway.
Hands-on activities can help children really see rainbows. You'll need to do them on a bright, sunny day, or have a source for white light. A prism makes it easy to see the full spectrum of the rainbow, as it bends the white light into the different colors. You might also give children a chance to make their own rainbow with a hose outside. The key to doing this is to have the sun behind them and the water in front, but see if students can figure this out on their own. Talk about your findings. Simply explain that light can bend and that a white light has many colors that separate when they bend.
In a rainbow, it's easy to see how colors mix together to form new ones. Give students colored, transparent plastic discs that they can use to mix colors. They'll see that, for example, if the light goes through a red and yellow disc, it will look orange. Point out how orange is between red and yellow on the rainbow.
Taking It Further
If your students are a bit older, you can take the lesson further by discussing wavelengths. The colors at the purple end of the spectrum have a higher wavelength than those in the red end of the spectrum. Students can understand that the light from the sun only appears white as all the colors come together. Once they're separated into individual wavelengths, students can see the different colors.
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