Rainbows form when sunlight interacts with water droplets in the air through two key processes: refraction and reflection. Here’s how it works:
- Sunlight enters a water droplet and slows down
- The light is separated into different wavelengths (colors)
- These colors reflect off the back of the droplet
- The separated colors exit the droplet at different angles
For us to see a rainbow, three conditions must be met:
- The sun must be behind the observer
- Water droplets must be present in the air
- The sun must be at a proper angle (usually 42 degrees)
This explains why rainbows often appear after rain when the sun comes out, and why they’re always in the opposite direction from the sun.