The pencil that looks bent
Put a pencil in a glass of water. It looks bent at the surface.
Step 1 of 4
- A coin lies at the bottom, really here.
- Two rays travel from it to the surface.
- They bend and leave, up toward the eye.
- Followed backward, they cross higher. The coin looks lifted.
The rule
Light bends where it goes from air into water. Light bends again where it leaves water. So a thing under water looks higher than it is. The thing has not moved.
The same bend makes a pond look shallow. The part of a pencil under water looks lifted. So the pencil looks bent.
Look from the side. The coin looks even higher.
Move your eye. See where the coin looks to be.
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