Use a water and a mirror to make a DANCING RAINBOW! This is such a fun rainbow science experiment that goes well with a science unit on light or the electromagnetic spectrum.
It’s also a fun activity to do for St. Patrick’s Day!
We did this science experiment with my middle school science class last week, and honestly my expectations were pretty low. However, it was awesome! My students thought the rainbow was super cool!
Supplies Needed for the Dancing Rainbow Science Experiment:
- A shallow container or baking dish
- A mirror – we used a square mirror from the craft store
- Rays of direct sunlight
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This experiment does not work with a flashlight. It also doesn’t work if your natural sunlight is just ambient light in the room. You need rays of sunlight shining directly onto the mirror!
When I did this lab with my science class, I was breaking one of the cardinal rules of teaching… the one that says TRY IT OUT FIRST! Haha! However, we did not have any sunshine on my preparation day. So I brought the materials to class and hoped for the best. I also brought a prism as a backup.
The rainbow that we made with the mirror and water was more impressive than the prism!
(However, if you plan to do this with a class, I would totally bring a prism too in case the sun is hiding behind clouds when you need it!)
How to Make a Dancing Rainbow:
Fill your container with enough water that you can submerge the mirror in the water.
Angle the mirror toward the sunlight as shown. It may take a little work to get it lined up right.
On the day that we did our experiment, we used a spot where sunlight was coming in through a hall window. It worked perfectly!
The water will be moving because of your hand adjusting the mirror. The moving water makes the rainbow dance! It looked like something from an animated movie – so cool.
We were able to get nice, thick areas with each color of the rainbow. The results were more impressive than with my prism!
The Science Behind the Dancing Rainbow:
In this experiment, sunlight travels through the water and reflects (or bounces) off the mirror. The reflected light travels back through the water and then speeds up as it travels through the air to the wall. This change in speed causes the light rays to be refracted or bent. As the light is refracted, white light is separated into the colors of the rainbow according to their wavelengths. Red light has the longest wavelength, followed by orange, yellow, green, indigo, and violet, which has the shortest wavelength of visible light. Science is so cool!
Need more science experiment ideas? We’ve got a huge supply of simple science experiments with materials you probably already have.
These Polarity of Water Science Experiments are so fun and colorful! It’s amazing what cool tricks water can do.