Lumi's Color Adventure

The big ideas

• White light is every color at once. A prism or a raindrop bends each color by a different amount, which spreads sunlight into a rainbow.

• Objects absorb some colors and reflect the rest. An apple absorbs most of the light that hits it and reflects mostly red, so red is what reaches your eye.

• White reflects almost everything; black absorbs almost everything. The absorbed light becomes heat, so dark clothes warm up in the sun.

• Eyes have three kinds of cone cells, most sensitive to reddish, greenish and bluish light. The brain compares their signals to make every color we see.

• Light adds, paint subtracts. Red, green and blue light combine toward white. Each paint absorbs some light, so mixing paints leaves less light and the mix gets darker.

• Air scatters blue light more than red. That scattered blue fills the sky, and at sunset the long path through the air leaves mostly orange and red.

Try it at home

1. Garden-hose rainbow On a sunny day, stand with the sun behind you and spray a fine mist.
2. Paint mixing Try yellow + blue, red + yellow and red + blue, then add white to each.
3. Find the pixels Look at a white part of a screen through a magnifying glass to spot tiny red, green and blue lights.
4. Sunny-day warmth test Put a white sheet of paper and a black one in the sun for ten minutes, then feel which one is warmer.

Ask after watching

• Why does a banana look yellow?
• What happens when you mix every paint?
• Why is the sky blue in the day and orange at sunset?