Grandpa Fenn's Workshop

The Periscope

There is a wall in the way and a bluebird on the other side. Grandpa has two mirrors and a long box. Toby says you cannot see around a wall.

Grandpa Fenn at the workshop door with his field notebook

Look over the wall

Tilt the top mirror and the bottom mirror until the light from the bird bends around the wall and reaches your eye.

A-
B-
C-

Grandpa peeks into the tube and nods. A wall, two mirrors, and a bluebird right where he left it.

Why it works

You see something because light from it reaches your eye. Light travels in straight lines. A wall stops it.

A mirror bounces light. The light leaves at the same angle it arrived. Two mirrors can send light around a corner, over a wall, or even up out of a submarine.

The trick is to lean both mirrors the same way, halfway between flat and upright. The top one turns light down the tube. The bottom one turns it toward your eye.

Grandpa. Light never bends on its own. It only bounces. Mirrors are just good at bouncing it where you want.
Toby FennToby peeks through

Grandpa's notebook

You see things when light reaches your eye.

Light travels in straight lines.

A mirror bounces light at the angle it came in.

Big word for the day. Reflect. To bounce back.

More machines are waiting on the bench.

Try the Shadow Clock

See Grandpa's Invention Wall

Back to the Chain Reaction Bench