Two years ago I ordered a batch of diffraction grating glasses to share with the kids in our lives. This year, I ordered a batch of Rainbow Peepholes to share instead. They are small cardboard circles with a center hole holding diffraction grating film which splits and diffracts light into several different beams radiating in different directions, making rainbow copies of your light source, such as candles, light bulbs, or Christmas trees. So if you hold one up to your eye and look at some Christmas lights, you’ll get a visual treat of an explosion of rainbows. They are a fun, inexpensive “treat” to share in the holiday season, costing 30 cents each if you get a batch of 100. If you order more than 100, the price goes down to 25 cents each, so ordering 120 is the same price as ordering 100–that is, if you order from Rainbow Symphony. You can purchase smaller quantities on other sites like eBay or Amazon, but the cost per unit is 50 cents. Do a little shopping around and go with the choice that will make sense for you.
You can also get Diffraction Grating Glasses for around 40 or 50 cents each here or here. The glasses work better for older kids and adults than they do for younger kids, because they don’t stay on little faces too well. For my preschoolers, I had to tape a paper strap in place in order to hold the glasses on their heads. So if you have little kids in mind for working with rainbow viewers, the peepholes may be a better choice. You can also get sheets of diffraction grating film, if you want to make your own projects.
To give as holiday treats, I typed up a brief note about what they were, fitting four to a page which I could then print, cut into quarter-pages, fold, and tape into envelopes to hold the Rainbow Peepholes. The text can read something like this:
Rainbow Peepholes have a diffraction grating film which splits and diffracts light into several beams traveling in different directions, so they make rainbows when you look at a light source, such as candles, Christmas lights, car headlights, fireworks, and so on. Have fun! Merry Christmas!
We gave one to each of Astronomonster #1’s classmates and handed them to friends and coworkers with kids.
This page from ScienceHouse.org recommends a simple home experiment with kids as young as first grade. So besides having fun with diffraction grating products to see rainbows all around, you can use them to “look at different light sources such as a black light, an infrared light, a full spectrum white light and a light for a photo lab and get them to make a drawing of each spectrum in their science journals and compare the spectra.”
While I’ve been giving them out for Christmas, you can also use them for watching fireworks, conducting light experiments, or giving them out at Halloween. If you have more ideas or projects with diffraction grating glasses or peepholes, please share them in the comments.