Why do rainbows form after rain?
Quick Answer
Rainbows form when sunlight enters raindrops, bends, reflects inside them, and bends again on the way out. Different colors exit at slightly different angles, creating the arc.
The Full Story
A rainbow is caused by refraction, internal reflection, and dispersion in water droplets. Sunlight splits into colors because each wavelength bends a little differently as it enters and leaves the droplet. The geometry means the brightest light reaches your eyes at about 42 degrees from the antisolar point for red light, with violet slightly inside that angle. This is why a rainbow appears opposite the Sun and usually after rain when droplets remain in the air.
Key Facts
YouTube Angle
Suggested video title for this topic:
"Why do raindrops turn sunlight into a rainbow?"
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