This is an incredibly simplified explanation, but: sunlight, though seemingly “invisible,” contains all the colors of the spectrum, from Douglas fir green to Rudolph’s nose red. If you’re looking to teach your students (or whoever) about light wavelengths and the electromagnetic spectrum and such, it can be difficult to illustrate this in a tangible way. You’re in luck, though, because we’ve got the perfect demonstration right here!
DIY Dark Side of the Moon
For this demo, you’ll need a sheet of paper (the bigger the better, but don’t go too crazy—there won’t be a football team running through it), a clear drinking glass (made of actual glass) roughly half full of water, and an open, fully sunlit outdoor space.
Bring all those stinky kids outside with you to your brightly lit location. Place the paper on the ground, using rocks or volunteers to hold it down—however you do it, just make sure there’s a decent-sized, uncovered space in the middle of it.
Then, hold the glass at the top with just your thumb and index finger, if possible. The key here is to not significantly block the sides of the glass while you’re holding it, or the experiment will be considerably more difficult. Hold the glass a few inches above the surface of the paper. Turn it, twist it, tilt it, raise it and lower it as necessary until a clear, colorful pattern appears on the paper.
From there, you’re free to tell your students you’re a mighty wizard who can conjure pure color from water. Or you can be super boring and give them the details detailed in the next section.
Go with the Wizard Story!
The glass of water works as a prism, refracting the light that enters it by essentially changing its direction. As the light enters the prism and refracts, the “white” light is split into the individual bands of color you see on the paper.
Using these properties of light wavelengths and their component colors, astronomers can determine the elements or gases that make up distant stars seen through their telescopes.
365 Simple Science Experiments with Everyday Materials, E. Richard Churchill, Louis V. Loeschnig, and Muriel Mandell, illustrated by Frances Zweifel, 2013. ISBN 978-1579129279