Scientific Thinking

When you see yourself in the mirror, the light bouncing off you is reflecting back to your eyes.

This is pretty straightforward, but things start to get more interesting when light is reflected more than once. If you've ever put two mirrors in the same room, you know that when the angle is just right, you can peer into an infinite abyss...

In this exploration, we'll use puzzles to unpack some fascinating optical effects.

House of Mirrors


Before we figure out optical puzzles with more than one mirror, we need to be clear about what happens to light at a single mirror.

You probably already know that a beam of light (like one from a laser) tends to follow a straight line. One case where it doesn't is when it encounters a mirror: instead of continuing straight, the beam of light is reflected. The precise direction of the reflected beam is determined by our first rule:

When a beam is reflected, the angle the incoming light makes with the mirror will always be equal to the angle the reflected light makes.

House of Mirrors


Light beams leave the gem in all directions, but only the beams that leave in some directions are seen by the eye.

Use the locator near the gem below to see where beams leaving in different directions end up. Where on the mirror can light beams reflect and enter the eye?

House of Mirrors


Select one or more

Someone hands you an open box with a hole on one side and invites you to look inside.

Little do you know that the person who built the box laid a mirror on one of the walls. The rest of the walls don't reflect light.

How many jewels can you see when your eye is at the center of the hole?