A simple periscope uses two mirrors
A tall wall hides the street. A periscope lets you look over the wall.
Step 1 of 4
- A bent tube. A tree is on one side. An eye is on the other.
- The top mirror turns the light down the tube.
- The bottom mirror turns it again, towards the eye.
- Each mirror is tilted at 45° to the light.
The new words
- Periscope — a tube for seeing over a wall. A simple one has two plane mirrors.
- Plane mirror — a flat mirror.
- Parallel — side by side, never meeting.
The rule
A simple periscope has two plane mirrors. They are parallel, each tilted at 45°. Light turns twice and reaches your eye.
Each mirror must send light along the next part of the tube. Tilt a mirror the wrong way. Then the light hits the side of the tube.
Each mirror follows the bounce rule. The light leaves at the same slant, or angle, as it arrived.
A mirror at 45° to the light turns it by 90°.
Never look at the Sun through a periscope or any mirror.
Now try it. Flip the mirrors until the eye sees the tree.
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