- magnifying glass
- white piece of paper or card stock
- computer or TV screen in a dark room
First, examine your magnifying glass. As you feel from one edge of the lens to the other, it bumps out. This means it's a convex lens. (If it dipped in, it would be a concave lens. An easy way to remember this is that a concave lens is shaped sort of like a cave.) Use your magnifying glass to get a better look at book covers, sand, your hair--everything around you! Notice that the magnifying glass only works when you hold it fairly close to the object you're trying to observe.
So why does it make things look bigger? Because the lens is bending the light from whatever you're looking at. And since it's a convex lens, it makes the light bend outward, and your eye sees a bigger image. You can find more information about how lenses work at sites like Optics for Kids and Activities in Optics.
Now for our magic trick. Take your magnifying glass and a piece of white paper or cardstock to a dark room with a TV or computer screen in it. Hold the paper about 3 feet from the screen with the magnifying glass against it. Now slowly move the magnifying glass away from the paper and toward the screen. (All three things--screen, magnifying glass, and paper--should be parallel to each other.) When you get it to just the right distance, you'll see the image from your screen projected on the paper--but upside-down and backwards. It's magic! :)
If you're not satisfied to leave this as a magic trick (and why should you be?), there's a great explanation of how it works here. This is the same "magic that's happening in projectors and even inside your own eyes! (Yes, your eyes have convex lenses too!)
See what other great (and preferrably safe) things you can do with your magnifying glass!