Blind-Spot Disappearing Dot
A visible mark disappears at a specific distance.
Teaching & key ideas
What you do: Close one eye and move card slowly until one mark vanishes.
What students see: A visible mark disappears at a specific distance.
Why it works: The optic nerve leaves the retina at a spot with no light receptors.
Question to ask: Where did the dot go?
Lesson flow
Predict → demonstrate → observe → briefly explain → ask: Where did the dot go?