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🌈 How do rainbows form

Follow sunlight through water droplets to see how refraction, reflection, dispersion, and your viewing angle turn rain into a bow of color.

lessons

~10 min

to learn

🔬 Science

subject

Adults

level

Start the course →

What you’ll learn

A Rainbow Needs Light, Water, and a ViewpointIdentify the Sun, suspended water, and observer geometry required for a primary rainbow and explain why the bow is part of a circle.A rainbow appears opposite the Sun when water droplets occupy the right viewing geometry; the visible arc is part of a circle.
Each Droplet Acts Like a Tiny Optical SystemTrace refraction, dispersion, internal reflection, and exit refraction through one raindrop.Each droplet bends, separates, reflects, and bends light again, while many droplets combine those paths into a bright pattern.
The Colors Reveal Wavelength and GeometryRelate color order, double rainbows, full circles, fogbows, and moonbows to wavelength, reflection count, droplet size, and viewpoint.Rainbow variations are readable clues about how light wavelengths and internal paths interact with droplets and the observer.

Questions this course answers

Which arrangement is most likely to let you see a primary rainbow?

A primary rainbow appears opposite the Sun, so the observer needs sunlight behind them and water droplets in front.

Put the main steps of a primary-rainbow ray in order.

The primary path includes refraction on entry, dispersion through the drop, one internal reflection, and refraction on exit.

Match each rainbow feature to the explanation that best fits it.

Color order, secondary bows, circular geometry, and fogbows each follow from a different part of the optical setup.

Why does a rainbow seem to move when you move, even though the rain cloud may stay in the same place?

A rainbow is an optical relationship rather than a fixed object with one location. Moving changes which rays can reach your eyes.

Grounded in trusted sources

National Weather Service, How Do Rainbows Form? — https://www.weather.gov/fgz/Rainbow
NOAA NESDIS SciJinks, What Causes a Rainbow? — https://scijinks.gov/about/k-12-education/optical-phenomena/what-causes-rainbow
Met Office, Rainbows: optical wonders — https://weather.metoffice.gov.uk/learn-about/weather/optical-effects/rainbows
NOAA National Weather Service Glossary, Rainbow — https://forecast.weather.gov/glossary.php?word=RAINBOW
NASA Picture Dictionary, Rainbow — https://www.nasa.gov/learning-resources/nasas-picture-dictionary-r/
NASA Earth Observatory, A Glorious View — https://science.nasa.gov/earth/earth-observatory/a-glorious-view-78380/

Every Wunder lesson is built from real, reputable sources — never invented.

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