There’s been talk of eliminating the penny from American currency for many, many years. There’re always plenty of compelling arguments for such—including the fact that it costs more than one cent to produce a new penny—and I for one wouldn’t miss them. At the very least, it seems like the treasury department or the mint or whoever could just stop making new ones and we could coast along on the pennies currently in circulation for quite a while—coins tend to last a long time.
With all that in mind, we present this easy peasy lemon squeezy Demo Science experiment that will demonstrates the reflection and refraction of light by water. Enjoy!
Swimmin’ Time with Abe Lincoln
For this one, you’ll need naught but a penny, a small dish (a saucer or small plate works swell), and some water. Ancillary supplies may include a towel to sop up any water spills, and possibly a tray or something on which to put the dish to contain said spills. Also, you’ll need a classroom and some students for whom to demonstrate, but those are gimmes.
Gather your students around your desk, and place the empty dish in the center of it. Lay the penny flat in the middle of the dish. Tell your students to keep their eyes on the coin while they slowly AND IN AN ORGANIZED FASHION (KEVIN!) back away from the dish. They should continue to retreat until the edge of the dish just barely blocks their view of the penny. Once they’ve reached this spot (which will vary from student to student, so instruct them to stay out of each other’s way), make sure they stay put as you continue the experiment. If they move, it’ll ruin the whole thing—for them; it’ll still look the same for everyone else who can follow instructions properly.
Now that the smelly little buggers are just past the threshold where the penny “disappears,” tell them that you will make it reappear via magic. The magic of science, that is!
Slowly pour water into the dish, and listen to the gasps of disbelief as the penny comes back into view. The taller kids will see it first, whilst your shorter students will have to wait for more water to be added. How the heck did you do that, teach?
How the Heck You Did That
The water in the dish causes light to refract. This allows the penny to be visible over the edge of the dish, as the light is bent by the rising water level on its way to the eyes of the viewer. Water can refract light in a variety of ways—it can also do essentially the exact opposite of this experiment and hinder our view of objects beneath the surface.