Cow's Eye Dissection - Experimenting with a Lens

Have you ever looked through a magnifying glass? The clear glass (or plastic) in a magnifying glass is a lens, like the lens that’s inside your eye.

Using the lens of a magnifying glass, you can bend light to make an image of the world. Look at the photo on the left. We used a magnifying glass to produce an inverted image of a candle. The photo on the right shows how.

You can try the same thing at home. For instructions on how to make an image with a magnifying glass, click here .

What’s Going On?
Suppose you use your magnifying glass to make an image of a tree on a sunny day. You hold your lens between the tree and a piece of paper. You move the lens to just the right spot. Voilà! There’s an image of the tree. That image is made of light.

Sunlight bounces off the tree and spreads out in all directions. Your lens gathers the light shining out in all directions from each spot on that tree and bends that light so it all comes back together on a single spot on your piece of paper. So light shining from a leaf at the top of the tree ends up on one spot on your paper. Light shining from a spot on the tree’s trunk ends up in a different spot on your paper. All these spots of light blend together in your eye to make an image.

This works because the lens in your magnifying glass is carefully shaped to bend light in a particular, predictable way. The lens is shaped to bend light rays so that they come together and then spread apart to make an image.
The lens of your magnifying glass is probably fat in the middle and thin at the edges. If you took the lens out of the magnifying glass, it would look like this:

The surface of this lens is curved. It’s that curve that makes light bend when it shines through your lens.

Learn more about lenses.