Invisible Glass in Oil
Parts of the glass seem to disappear.
Teaching & key ideas
What you do: Lower the glass into the oil.
What students see: Parts of the glass seem to disappear.
Why it works: When two materials bend light by nearly the same amount, their boundary becomes hard to see.
Question to ask: Where did the edge go?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: Where did the edge go?