Dropping a coin in water usually results in it sinking due to its higher density compared to water. However, several interesting experiments and illusions can be created using coins and water, demonstrating the principles of light refraction and surface tension:
- What it shows: Light refraction.
- How to do it: Place a coin on a flat surface and cover it with an empty, clear glass. Observe the coin through the side of the glass. It should be clearly visible. Slowly pour water into the glass while observing from the side. As the water fills the glass, the coin will appear to vanish. If you look from the top, you’ll still see it.
- Explanation: When light travels from one medium (like air) to another (like water), it changes speed and direction, bending or refracting. When viewed from the side, the light rays from the coin passing through the water bend so much that they no longer reach your eyes, making the coin appear to disappear.
- What it shows: Surface tension.
- How to do it: Carefully balance a coin on a bent paperclip and slowly lower it onto the water surface in a bowl or glass. Gently remove the paperclip. The coin should remain floating.
- Explanation: Surface tension is the cohesive force that holds water molecules together at the surface, creating a thin, elastic-like layer. This layer is strong enough to support the weight of a light object like a coin, creating a slight indentation on the surface where the coin rests.
- What it shows: Light refraction.
- How to do it: Place a coin at the bottom of a glass or bowl. Fill the container with water and observe the coin from various angles. You might notice that the coin appears to be higher than its actual position, or even that you can see two images of the coin when viewed from certain angles.
- Explanation: When light from the coin travels from the water (denser medium) into the air (rarer medium) and then into your eyes, it bends away from the normal (an imaginary line perpendicular to the water surface). This bending of light, or refraction, makes the coin appear to be in a shallower or different position than its actual location.
These simple experiments demonstrate how the properties of light and water can create fascinating visual illusions, offering a fun and engaging way to explore basic scientific concepts.
Do coins in water stop flies?
Great question! Keep flies way for just a few pennies. Some coins in a baggie of water will get rid of these pests.