The Invisible Eyes
Two friends explain the invisible beam that stops a closing garage door and sends it back up.
Listen to this lesson
Read aloud by Smorty and the lantern firefly.
The Dessert Idea
A shadow shows that something blocked the light.
The Door Idea
Two sensors near the floor send an invisible beam across the door; if anything blocks it, the door stops and goes back up.
The Lesson
Smorty: Down at the bottom of the track there are two little eyes, one on each side.
Firefly: They shine an invisible light to each other, across the doorway.
Smorty: If something steps through, the light is blocked, so the door stops and goes back up, to keep everyone safe.
Firefly: A door that will not close might not be broken. It might just be keeping you safe.
Told by Smorty and the lantern firefly
Try It With a Grown-Up
Shine a flashlight across a table at a wall and hold your hand in the beam. The shadow is the light being blocked. The door's eyes notice the same thing with a beam you cannot see.
Keep Exploring
This button opens another site, about how real garage doors work. Ask a grown-up first.
Learn more about real garage doors