This easy disappearing coin trick uses refraction of light to make it look like a coin under a glass disappears!
Glass cup or jar
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.
Why does the coin disappear?
Light (from the sun, or an artificial light) travels in a straight line, bounces off objects and into 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 in this activity the light is refracted ( bends ) and doesn’t make it to 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.
Suitable for Key stage 2 Science
Light travels in straight lines