The Rainbow Angle

Why 42°?

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Light piles up at the maximum exit angle: about 42° from the antisolar point.
• Red is outside (42.4°) and violet inside (40.6°).
• The rainbow is a set of directions, not an object: it moves with you.

Steps

1. Light in a raindrop
2. Descartes traces the rays
3. Where the light piles up
4. Chasing the rainbow
5. Morning and evening
6. How high is the arc?
7. No rainbows at noon