Disappearing Coin Trick - Refraction Demonstration

Here at Science Sparks, we love science tricks and super simple science experiments. This disappearing coin trick is both!

The trick uses refraction of light to make it look like a coin under a glass disappears!

Impress your family and friends with this simple science magic trick and learn about light at the same time!

How to make a coin disappear

Materials

Glass cup or jar

Coin

Water

Instructions

Place a glass on top of a coin and ask a friend if they can still see the coin. Hopefully, they will say yes!

Pour water into the glass and ask your friend if they can see the coin now. They should say that the coin has disappeared.

empty glass of water for a refraction of light experiment.

Why does the coin disappear?

Light (from the sun or artificial light) travels in a straight line, bounces off objects, and enters our eyes, allowing us to see things. Generally, there is little or no refraction of light as it travels through air.

However, when you pour water into the glass or jar, the light from the coin is refracted ( bends ) and doesn't reach your eyes, which is why the coin seems to disappear.

Did you know that the retina at the back of your eye contains over 120 million rods and 8 million cones?? Rods detect light and dark, and cones allow us to detect colour.