Science & Math How light and water make rainbows
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Image 1. When light from a distant source, such as the sun, strikes a collection of water drops, a rainbow might appear. Photo by: James Wheeler via Pexels By Encyclopædia Britannica LaunchPacks, adapted by Newsela staff Published:12/04/2019 Word Count:449
Rainbows have many beautiful colors. They are red, orange, yellow, green, blue and violet.
You can see a rainbow when sunlight hits water drops. Rainbows have a curved shape called an arc.
The ends of the rainbow seem to touch the Earth.
Yet rainbows cannot be seen all the time. The person watching has to be between the sun and the water drops. But the rainbow is not in one spot in the sky. Its position seems to change. It depends on where the light source is. It also depends on where the person watching is. Rainbows are most often seen in early morning. They can also be seen sometimes in late afternoon.
That is when the sun is lower in the sky. Part of the arc can be seen. No rainbows appear when the sun is high in the sky.
Image 2. The appearance of a rainbow depends on the angle at which the sun's light rays are refracted (bent) and reflected by droplets of water suspended in the air. Red is refracted least and violet is refracted most. Thus, in the bright primary bow, red is on the outside and violet on the inside. When a dimmer secondary bow occurs, the colors are reversed. Photo by: Encyclopædia Britannica, Inc
We See Only Some Colors Rainbows happen because of how light acts. Light is a type of energy. It behaves as a wave does. You can measure the distance between two peaks or highest points of a wave. It is called the wavelength.
We see different wavelengths as different colors.
Light hits different objects. Some wavelengths are reflected. This means they bounce back. This is the color we see. Yet humans cannot see all wavelengths. We can see only a certain range. The range is called the visible spectrum. White light is all the colors of this spectrum.
Sunlight Splits The Different Wavelengths
When white sunlight enters a raindrop, the light rays bend. This bending is called refraction. It splits the different wavelengths of light. The separated colors are then bounced back toward the person watching.
The rainbow you see is called a primary rainbow. The colors are in order from inside to outside. The order is violet, blue, green, yellow, orange and red. Sometimes a second rainbow is visible. This is called the secondary bow. It is usually very faint. Its color sequence is reversed.
Sometimes, raindrops are extremely small. They almost look like mist. These drops produce a bow that is almost white. This is called a fogbow or a lunar rainbow. Fogbows sometimes appear at night.
They look like a ring around the moon. They are made by sunlight reflected from the moon.
This article was originally published by Encyclopaedia Britannica, Inc. Newsela adapted the original article and is responsible for all revisions and for any errors that may result from the adaptation. Annotation
Jenna Peebles
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