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Question of the day Science & Nature

How Rainbows Form: Light, Water, and Color Explained

Short answer

Sunlight bends, reflects, and separates inside raindrops

A rainbow forms when sunlight enters water droplets, bends and separates into colors, reflects inside the droplets, then bends again as it exits. The colors reach an observer from droplets in a particular direction, making a curved arc.

What bends
Sunlight changes direction in water
Color order
Red is outside, violet inside
Viewing angle
The Sun stays behind you

Read the full answer 6 min read · Further reading: NOAA National Weather Service

  • 455 answers
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  • Each one names where to read more

Start here

Twelve good first questions, each with its short answer.

  1. 1
    How Wi-Fi Works: Signals, Routers, and ConnectionsWi-Fi sends data between devices using radio wavesTech & Apps · 8 min
  2. 2
    Two-Factor Authentication: How It Works and Why It MattersA second proof of identity for signing inTech & Apps · 7 min
  3. 3
    How to Get Rid of Fruit Flies and Keep Them AwayRemove breeding spots and trap adult fliesHome & Garden · 8 min
  4. 4
    How Long to Boil an Egg? Timing for Every YolkBoil eggs for 6 to 12 minutesFood & Kitchen · 7 min
  5. 5
    How to Season a Cast Iron Skillet ProperlyApply a thin oil coat and bake it onto the skilletFood & Kitchen · 7 min
  6. 6
    Why Is the Sky Blue? Rayleigh Scattering ExplainedAir scatters blue sunlight more than red sunlightScience & Nature · 7 min
  7. 7
    How Rainbows Form: Light, Water, and Color ExplainedSunlight bends, reflects, and separates inside raindropsScience & Nature · 6 min
  8. 8
    What Does RSVP Mean? The French Phrase ExplainedRSVP means please respond to an invitationWords, Holidays & Traditions · 7 min
  9. 9
    W-2 Form: What It Shows and How It WorksA wage and tax statement from your employerMoney & Work Basics · 7 min
  10. 10
    What Does the Check Engine Light Mean?It signals a detected engine or emissions-system problemCars & Travel · 7 min
  11. 11
    Why Do Cats Purr? What the Sound Can Tell YouCats purr to communicate and regulate their statePets & Animals · 6 min
  12. 12
    How Often Should You Bathe a Dog? A Practical GuideUsually every few weeks, or when dirtyPets & Animals · 7 min

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  1. One real questionEach page takes one question people type into search, such as why the sky is blue or how long to boil an egg.
  2. The short answer firstA one-line answer, a two-sentence explanation and three key facts sit at the top, before any detail.
  3. Where to read moreEvery answer names the organisation that covers the topic, such as USDA FoodSafety.gov, NASA, the National Weather Service or Merriam-Webster.