1. Introduction: The Coin That Reappears
Place a coin at the bottom of an empty steel bowl. Step back until the coin just disappears below the rim — you cannot see it anymore.
Now ask someone to slowly pour water into the bowl without moving the coin.
The coin comes back into view. Nobody touched it. Nobody moved the bowl. The coin did not float up. Yet you can see it again.
Something happened to the light travelling from the coin to your eyes. The water changed the path of that light. That "something" is refraction.
You can now describe refraction as a real event you have seen — not just a word from a textbook.