This is something to watch for on a sunny, hot summer day. When you happen to be on a long, straight road, take a look at the surface of the road up ahead of the car. It often appears that there are pools of water on the road. You may even see the “reflections” of cars in these “pools.”

When you drive closer to these “pools,” you will see that they disappear. You have been the victim of a mirage. This is the same illusion that fools many thirsty wanderers in the desert.

Glass and water are not the only substances that can bend light. The temperature of the air affects the speed of light also. When light travels through air of one temperature into air of another, its speed changes, and the light bends.

The air near the ground is much hotter than the air higher up. Light that is coming from above is refracted when it meets this hotter air. Instead of continuing in its path toward the road, the light is bent up toward your eyes. You see an image of the blue sky where you would normally see the road. It looks as if the road is covered with a pool of water. Often you can see what appears to be the reflection of the car as if the car is driving on water. This is not a reflection at all, but a bending of the light as it meets different air temperatures.

To find this experiment and many more please read Light Action! Amazing Experiments with Optics by Vicki Cobb and Josh Cobb, illustrated by Theo Cobb. To purchase a copy click here.