This might be one of the most simple to set up science experiments we’ve ever tried. It is a bit tricky to explain, but impressive even if you can’t quite get your head around it!

If you like this activity don’t forget to check out out our other easy science experiments for kids.

Materials for Light Refraction Experiment

Paper or card





Fill the glass almost to the top.

Light Refraction Experiment with arrows and water

Draw arrows on one piece of of card or paper. Place the paper behind the glass and watch as the arrow points the other way.

Refraction experiment

Now try to think of a word that still makes sense if you put it behind the glass.

We tried bud, the green ( badly drawn ) plant is on the opposite side when the paper is not behind the glass.

NOW works well too 🙂

refraction experiment
Refraction activity

How does this work?

Refraction ( bending of light ) happens when light travels between two mediums. In the refraction experiment above light travels from the arrow through the air, through the glass, the water, the glass again and air again before reaching your eyes.

The light reaching your eye (or in this case our camera) coming from the arrow is refracted through the glass of water. In fact the glass of water acts like a convex lens (like you might have in a magnifying glass). Convex lenses bend light to a focal point. This is the point at which the light from an object crosses.

The light that was at the tip of the arrow is now on the right side and the light on the right side is now on the left as far as your eye is concerned (assuming you are further away from the glass than the focal point.

If you move the arrow image closer to the glass than the focal point it will be the way around you expect it to be!

More Refraction experiments

Find out how to make your own magnifying glass.

We’ve also got a fun disappearing coin trick.

Or try our light maze to learn about reflection.

How to make a light maze

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Originally posted at Science Sparks