Soldiers, submarines, and spies have used periscopes for centuries to see around corners and over walls. Build your own from a cereal box and 2 mirrors!
What You’ll Need
📦 An empty cereal box (or any tall narrow box)
🪞 2 small mirrors (any size that fits the box width)
📏 Ruler
✏️ Pencil
🛠️ Scissors or craft knife (with adult help)
🧷 Tape
🎨 Markers or paint (optional, to decorate)
How to Build It
1. Open your cereal box at the top and the bottom flaps.
2. On the FRONT of the box, near the TOP, cut a square opening big enough for your eye to peek through.
3. On the BACK of the box, near the BOTTOM, cut a similar opening.
4. Inside the box at the top, tape the first mirror at a 45-degree angle — facing the top opening, reflecting downward inside the box.
5. Inside the box at the bottom, tape the second mirror at a 45-degree angle — facing the bottom opening, reflecting upward toward the first mirror.
6. Close up the box (tape the flaps shut).
7. Hold it up — look through the BOTTOM hole, and you’ll see what’s at the TOP! 🤩
How It Works: The Power of Reflection
Light bounces off mirrors at the same angle it hits them. If light comes in straight, it bounces straight back. If it hits at a 45-degree angle, it reflects at a 90-degree turn!
Your periscope uses this trick twice:
1️⃣ Light from above enters the top hole
2️⃣ Mirror 1 bounces it 90° downward
3️⃣ Light travels down the tube
4️⃣ Mirror 2 bounces it 90° toward your eye
5️⃣ You see what’s at the top of the box!
Real-Life Periscopes
🚢 Submarines — long periscopes let the crew see above water
🪖 Soldiers — peek over walls without exposing their head
🚂 Old tanks — see outside without opening the hatch
🚗 Modern cars — rear-view mirrors are mini periscopes!
Fun Periscope Challenges
🔍 Make it long enough to see over a wall in your room
🌽 Hide behind a couch and spy on your family
📐 Try different mirror angles — what happens to the image?
Engineering through reflection — now you can see around corners! 👀
