If any of your students have ever gone swimming (judging by the smell, some of those little buggers have seemingly never been in water of any kind), they’ve probably noticed that water can create optical illusions. The main cause of these illusions is light refraction, which is affected by the medium through which light travels. Because light is necessary for us to see things, changes in the way it travels can affect what we see.
Since a swimming pool—portable or otherwise—is not an easy supply to procure for a silly little science experiment, we offer this handy dandy alternative that will help you demonstrate water’s effects on light refraction.
DIY Mini Swimming Pool, a.k.a. A Glass of Water
For this Demo Science science demo, all you’ll need are a clear drinking glass, water to fill said glass, and a drinking straw. Fill the glass roughly half full, then place the straw in the glass. DO NOT put the straw in before you pour in the water, or the whole thing will be ruined. Just kidding: it makes no difference whatsoever.
Have your students observe the results, studying the straw from the top, bottom, and sides. Have them record their observations on paper. Give them a while to take notes and such, then compare and contrast the students’ findings. What did they see and/or discover?
The Straw that “Broke”
When looking at the straw through the sides of the glass, student likely noticed that it looks like it’s bent or broken at the water’s surface. It’s not, of course—that’s just refraction in action!
The straw appears askew because light rays travel through glass, water, and other mediums more slowly than they do through air. Ergo, the light rays that give your eyeballs a view of the part of the straw that’s out of the water arrive prior to those providing the image of the part that’s in the water. (Both are equally affected by the surrounding glass, so that’s a wash.) This gives the illusion that the straw is broken or bent.