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Color and Light · entry 2 of 52
Rainbows form when sunlight bends and reflects inside countless tiny water droplets in the air.
The longer version
Sunlight entering a falling raindrop slows and bends as it crosses into water, bounces off the inner back surface, then bends again on the way out. Because each wavelength leaves at a slightly different angle, the drop fans white light into a band of colors aimed back toward the sun's opposite side.
Millions of drops contribute at once, each sending only one color toward an observer's eye, which is why the arc looks continuous rather than dotted. The classic bow sits about 42 degrees from the point opposite the sun. Spray from a hose or waterfall can produce the same effect on a small scale.
Where this entry sits
These facts explore how light behaves and how human eyes turn it into the colors we see. Along the way you meet rainbows, prisms, mirrors, shadows, lasers, and optical tricks that fool our vision every day. The full list sits on the Color and Light page, where every entry is listed in order.
More From Color and Light
Eight more entriesA prism splits white light into a spectrum because each wavelength bends by a different amount.
Read 4Shadows appear when an opaque object blocks light from reaching a surface behind it.
Read 5Mirrors reflect light because a thin metal coating bounces most incoming rays straight back.
Read 6A red apple looks red because its skin absorbs most colors and reflects red wavelengths.
Read 7White objects look white because they reflect nearly all wavelengths of visible light equally.
Read 8Black surfaces look dark because they absorb most of the visible light that falls on them.
Read 9Sunlight contains all the colors of the visible spectrum blended together into white light.
Read 10Violet light has the shortest wavelength visible to humans, while red has the longest.
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