How to Build a Working Periscope with Your Kids

Learn to create a simple periscope using household materials that actually lets you see around corners and over obstacles.

  1. Gather Your Materials. You'll need a tall, narrow box (like a cereal box or oatmeal container), two small mirrors (craft mirrors work perfectly), strong tape or glue, a ruler, pencil, and scissors or box cutter. The mirrors should be roughly 2-3 inches wide and fit comfortably inside your container. If you don't have mirrors, you can use reflective material like polished metal or even smartphone screen protectors in a pinch.
  2. Prepare Your Container. Cut two square holes in your container - one near the top on one side, and another near the bottom on the opposite side. Each hole should be slightly smaller than your mirrors. The top hole lets light in, and the bottom hole is where you'll look through. Make sure the holes are on opposite sides of the container, not the same side.
  3. Position the Mirrors Correctly. This is the crucial step that makes your periscope actually work. Place the first mirror inside at the top, angled at exactly 45 degrees, facing down toward the bottom hole. The second mirror goes at the bottom, also at 45 degrees, but facing up toward where your eye will be. The mirrors should be parallel to each other but facing in opposite directions. Light enters the top hole, hits the top mirror, bounces down to the bottom mirror, then reflects into your eye.
  4. Secure Everything in Place. Once you've got the angles right, tape or glue the mirrors firmly in position. Test your periscope by looking through the bottom hole - you should see whatever is in front of the top hole. If you see mostly darkness or weird angles, adjust the mirror positions until the view is clear. The mirrors must stay at that 45-degree angle for the light to bounce correctly.
  5. Test and Improve Your Design. Try using your periscope to look over a fence, around a doorway, or under a table. If the image seems dim, make sure your mirrors are clean and the holes are big enough. You can decorate the outside of your periscope with paint or stickers, but avoid getting anything on the mirrors themselves. For better durability, reinforce the corners with extra tape.