Coin Appears When Water Is Added
The coin appears.
Teaching & key ideas
What you do: Position viewer so rim hides coin, then add water without moving viewer.
What students see: The coin appears.
Why it works: Light bends at the water-air boundary, changing the apparent position.
Question to ask: Did the coin move?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: Did the coin move?