How does light let you see these words? Here’s how:

Suppose you’re looking out the window on a sunny day and you see a tree. You see that tree because light from the sun hit that tree. Some of that light reflected from the tree—it bounced off the tree like a ball bouncing off a wall.

Some of that reflected light hit you right in the eye. That reflected light goes through the clear cornea of your eye. As it goes through the cornea, it bends a little.

The light shines through your pupil, the dark hole in the middle of your eye.

The light shines through the lens of your eye. The lens in your eye bends the light that has reflected from that tree to make a perfect little upside-down picture of the tree on the back of your eyeball. (Find out more about lenses and how bending light makes pictures.)

Light and your eye

At the back of your eyeball, there’s a layer of cells that are sensitive to light called the retina. When the picture of the tree shines on the retina, the light-sensitive cells send messages to your brain.

Your brain takes the information from your retina and puts it together to make an image of the tree in your mind.

Weird, isn’t it? You think you see the tree—but what you see is the light that bounced off the tree and got into your eye. Or if you really want to get picky, what you really see is the fixed-up picture that your brain makes up from the mixed signals it gets from your eye. Amazing!

You can experiment to find out more about how your eye works here.

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