What Happens When Light Hits Things?

Now think about a piece of paper. If you hold it up to a lamp, you can see a little bit of light — but everything looks blurry.

• Why can you see through some things but not others?
• What do you think light does when it hits something?

Light travels in a straight line. When light hits something, different things can happen. It depends on the material — that means what the object is made of.

Scientists learn about things by testing them. We can be scientists too! Let's plan a test to see what happens when light hits different materials.

Test What Happens to Light

What you need: A flashlight, and some things to test — like clear plastic wrap, wax paper, a piece of cardboard, a book, a glass of water, and a piece of cloth.

• Pick one item. Hold it up in front of you.
• Shine the flashlight on one side of the item.
• Look at the other side. Can you see the light? Write or draw what you see!
• Try the next item. Do the same thing. Is it the same or different?

What to watch for: Does the light go all the way through? Does only some light get through? Or does no light get through at all?

When we shine light on different things, we see that each material does something different!

Clear things like glass and plastic wrap let all the light through. We can see clearly through them. Some things like wax paper and thin cloth only let a little bit of light through. Things look fuzzy. And thick, dark things like cardboard and wood don't let any light through at all.

This helps us understand why we use glass for windows! Glass is transparent, so light comes in and we can see outside. Walls are opaque, so they block the light and give us privacy.

Scientists look for cause and effect. That means: when you do something, something else happens because of it.

Here is the pattern we found: what a thing is made of causes light to do different things. The material is the cause. What happens to the light is the effect.

This same pattern shows up everywhere! When you put on sunglasses, they are a little translucent — some light comes through but not all. When you pull down a window shade, it's more opaque — it blocks the light so you can sleep.

People use what they know about light to solve problems every day!

Can You Build a Better Fort?

Imagine you want to make a dark reading fort. You need to block the light! What materials would you pick? Think about what you learned. Would you pick clear wrap or a thick blanket? Why?

Now imagine you want a fort that lets a little light in so you can read. What would you use instead?

• Light — Energy that lets us see things. It comes from the sun, lamps, and flashlights.
• Material — What something is made of, like wood, glass, or paper.
• Transparent — A material that lets all light go through. You can see clearly through it. (Glass, clear water)
• Translucent — A material that lets only some light go through. Things look blurry through it. (Wax paper, frosted glass)
• Opaque — A material that blocks all light. You cannot see through it at all. (Cardboard, a wall)