An Arc of Light

What causes rainbows?

1 Almost every culture has stories and legends about the large arcs of color that stretch across the sky when weather conditions are right. Irish folklore tells of leprechauns hiding pots of gold at the end of the rainbow. Chinese mythology explains rainbows as openings in the sky that have been sealed by a goddess using stones of seven different colors. In Hindu mythology, a rainbow is viewed as the bow of the god of thunder and lightning. Rainbows even appear in popular modern culture. Remember Dorothy singing “Somewhere Over the Rainbow” in The Wizard of Oz?

2 Rainbows enchant and mystify people because they are beautiful but fleeting. Conditions must be exactly right in order for rainbows to form. They are usually seen at the end of a rain shower, on the opposite side of the sky from the sun.

3 Although sunlight appears to be white, it is actually made up of all the colors in the spectrum. When sunlight enters a raindrop, it is bent, or refracted, and the light’s individual strands of color become visible. The wavelengths of different colors vary, which is why each color bends slightly differently to produce the bands of color known as a rainbow.

4 Rainbows are usually described as comprising seven colors: red, orange, yellow, green, blue, indigo, and violet. An acronym for remembering the order of the colors is the name ROY G. BIV, in which each letter stands for a color in the spectrum.

5 Several people may see a rainbow at the same time, but they are not all seeing the same rainbow. Rainbows don’t exist at an exact location in the sky, and the way they appear is dependent upon a specific point. Each of your eyes even perceives a rainbow slightly differently. This means that you’ll never see the exact same rainbow as someone else, unless you are looking at a photograph!

6 Rainbows are always seen during the day because they require sunlight to form. However, it is possible to see a moonbow, or a nighttime rainbow, on nights when the moon shines particularly brightly. A moonbow is formed in the same way a rainbow is, but it is not nearly as bright. In fact, it appears to be whitish in color because the human eye cannot discern bright colors in dim light.

7 If weather conditions have not been right for you to spot a rainbow in the sky, you can make your own at home or at school. You’ll just need a large, clear, circular glass or jar of water, a small mirror, and a flashlight. Place the mirror in the water and tilt it slightly upward. Go into a completely dark room that has white walls, and shine the flashlight on the mirror. You’ll be able to see a colorful rainbow you created yourself.

Spectrum Reading Grade 6

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1. The Latin root spec means see. Find a word in paragraph 3 with the root spec.

2. The Latin root fract means break. Find a word in paragraph 3 with the root fract.

3. The Greek root photo means light. Find a word in paragraph 5 with the root photo.

4. Why do each of the colors in a rainbow bend slightly differently?

5. What is one way to remember the order of colors in a rainbow?

6. Why does a moonbow appear to be whitish in color?

7. What materials do you need to create your own rainbow?

8. What is the only way to see exactly the same rainbow someone else sees?

9. How are a rainbow and a moonbow different? How are they similar?

Write T before the sentences that are true. Write F before the sentences that are false.

10. _____ Leprechauns hide pots of gold at the end of the rainbow in Chinese mythology.

11. _____ Sunlight is made of all the colors in the spectrum.

12. _____ Most rainbows are seen on snowy days when the temperature dips below freezing.

13. _____ Everyone looking at a rainbow will see exactly the same image of a rainbow.

14. _____ Dorothy is a character in The Wizard of Oz.

Spectrum Reading Grade 6

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