Disappearing Coin Trick (Refraction)

Placing a glass of water over a coin makes the coin appear to vanish. This happens because light bends, or refracts, when it travels from air into water, preventing light from the coin from reaching the viewer’s eyes.

1. Place a coin on a flat surface.
2. Put an empty glass or jar directly over the coin. Ask a friend if they can still see it (they should answer yes).
3. Slowly pour water into the glass while keeping it over the coin.
4. Ask again if they can see the coin. The coin should now appear to disappear.

Disappearing Coin Experiment (REFRACTION OF LIGHT) - I Love Fun Science:

Disappearing Coin Trick - Dr Boyd The Chemist:

📄 Disappearing Coin Trick - Refraction Demonstration - Science Sparks: https://www.science-sparks.com/disappearing-coin-trick/

• Try using different shapes or sizes of glass containers to see if the effect changes.
• Place the coin at different positions under the glass (centered vs. off to the side).
• Repeat with other small objects (e.g., a button) to test whether the effect is the same.

• Handle glass carefully to avoid breakage.
• Clean up spills promptly to prevent slipping.

• Why does the coin disappear when water is added? (Light is refracted by the curved surface of the glass and water, so light from the coin no longer reaches your eyes.)
• Does the coin really disappear? (No, it is still there, but the light path is bent so you cannot see it.)
• How does this relate to other real-world examples of refraction? (Objects appear bent in water, rainbows form from light splitting in raindrops, lenses in glasses and cameras bend light to focus images.)
• What happens if you look at the glass from above instead of the side? (The coin is visible again, because light is no longer refracted away from your eyes.)