Beam Bounce

The big ideas

What the levels teach, in grown-up words.

• Light travels in straight lines. A beam keeps going straight until something stops it or bounces it. That is why a rock blocks the light and why shadows have sharp edges.
• Mirrors reflect light at the same angle it arrives. A mirror tilted at 45 degrees turns a beam by exactly 90 degrees, which is what makes the puzzles predictable.
• Colored glass is a filter. Red glass lets red light through and absorbs the rest. Put red glass and green glass in a row and almost no light gets through, because each one removes what the other lets pass.
• Colored light adds up. Red light plus green light looks yellow, and red plus green plus blue looks white. Phone and TV screens make every color from tiny red, green and blue lights.
• A prism spreads white light into a rainbow. Glass bends each color by a slightly different amount, so the colors fan out. A prism cannot make a rainbow from light that is only red.

Try it at home

Quick experiments that match the game.

1. Flashlight tag. In a dark room, bounce a flashlight beam off a hand mirror onto the ceiling. Tilt the mirror a little and watch how far the spot jumps.
2. Colored glass. Look through a piece of red cellophane or a colored candy wrapper. Which things keep their color and which turn dark?
3. Mix light. Shine two flashlights covered with red and green cellophane onto the same white wall. Where they overlap, look for yellow.
4. Make a rainbow. Hold a glass of water in a sunbeam near a white wall, or spray a hose mist with the sun behind you, and look for the colors.