Why the Sky Is Blue

Rayleigh scattering

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Rayleigh scattering by molecules goes as $1/\lambda^4$: blue scatters most.
• Long paths through air at sunset leave red and orange.
• Big droplets scatter all colours equally, so clouds are white.

Steps

1. Scattering by molecules
2. Four times as strong
3. Violet versus red
4. Red sunsets
5. Why not violet?
6. White clouds