How can two mirrors help someone see over a wall?

A wall can hide a whole garden, even when you stand on tiptoe. But a mirror, a smooth surface that bounces light back, can help with a clever peek. How can two mirrors help someone see over a wall?

The secret starts with light, the brightness that lets you see things. In the garden, sunlight lands on a yellow flower and bounces away in many directions. You see the flower when some of that light reaches your eyes.

Light travels in straight lines until something gets in its way or changes its direction. A solid wall blocks the light traveling from the flower toward your eyes. You need a way for that light to reach you around the wall.

Someone can use a periscope, a looking tube with mirrors that help you see past something in your way. A simple periscope has two mirrors inside, one near the top and one near the bottom. Each mirror gives the light a turn.

The person holds the periscope with its top peeking above the wall. An opening at the top faces the garden, so light from the flower can enter. The upper mirror sits just inside that opening.

That upper mirror sits at a slant, halfway between lying flat and standing straight up. Can you guess where it needs to send the flower's light: down the tube or up toward the clouds? The person is waiting at the bottom.

Down the tube! The flower's light hits the slanted upper mirror and bounces downward. The tilt matters because it turns light coming in from the garden toward the lower mirror.

Near the bottom, the second mirror sits at a matching slant, with its shiny side catching the light from above. It turns that downward-traveling light sideways. Now the light heads toward a small opening on the person's side of the tube.

The person looks through that lower opening, and the flower's light reaches their eyes. They see the flower even though the wall still stands in front of them. The two mirrors have given the light a path around the wall.

The person can keep both feet on the ground while looking through the periscope. Only its top needs to reach above the wall, with a clear view of the flower. The mirrors keep bouncing the flower's light along the same two-turn path.

Sunlight, flower, light, upper mirror, down the periscope, lower mirror, eyes. Two tilted mirrors help someone see over a wall by bouncing light from above the wall down and then into their eyes.

Now you know how two little turns can bring a hidden flower into view.