Why rainbows occur

Posted in: Weather. Posted on: 28 April A lovely painting of a rainbow by one of the RMetS staff children Rainbows are one of the most admired meteorological phenomena across the globe, but how are they formed? However, for the observer to see a rainbow, they must be in a specific position relative to the sun and water droplets - The observer must be positioned so the sun is behind them.

Water droplets such as rain or fog must be in front of the observer. The nine-hour rainbow Credit: Chinese Culture University You can usually see rainbows in the sky for an hour. Categories: Weather. You can see rainbows when the sun is located right behind you. The main rainbow becomes visible at an angle of around 40" from the horizon.

You can see the auxiliary rainbow at about 53". The orders of the colors reflected from the water droplets in the main rainbow and in the auxiliary rainbow are reversed, as shown in the illustration. Chapter 1: The Mysteries of Light. Why Is the Sky Blue? How Do Rainbows Form? Why Light Fades in the Bathroom? Why Do Water Surfaces Shine? Why Do Comets Have Tails? As the light passes into the droplet, the light bends, or refracts, a little, because light travels slower in water than in air because water is denser.

Then the light bounces off the back of the water droplet and goes back the way it came, bending again as it speeds up when it exits the water droplet. Light enters a water droplet, bending as it slows down a bit going from air to denser water. The light reflects off the inside of the droplet, separating into its component wavelengths—or colors. When it exits the droplet, it makes a rainbow.

Sunlight is made up of many wavelengths—or colors—of light. Some of those wavelengths get bent more than others when the light enters the water droplet.

Violet the shortest wavelength of visible light bends the most, red the longest wavelength of visible light bends the least. Many scientists, however, think " indigo " is too close to blue to be truly distinguishable. White light is how our eyes perceive all the colors of the rainbow mixed together. Sunlight appears white. When sunlight hits a rain droplet, some of the light is reflected.

The electromagnetic spectrum is made of light with many different wavelength s, and each is reflected at a different angle. Thus, spectrum is separated, producing a rainbow. Red has the longest wavelength of visible light, about nanometer s.

It usually appears on the outer part of a rainbow's arch. Violet has the shortest wavelength about nanometers and it usually appears on the inner arch of the rainbow. At their edges, the colors of a rainbow actually overlap. This produces a sheen of "white" light, making the inside of a rainbow much brighter than the outside. Visible light is only part of a rainbow. Infrared radiation exists just beyond visible red light, while ultraviolet is just beyond violet.

There are also radio wave s beyond infrared , x-ray s beyond ultraviolet , and gamma radiation beyond x-rays. Scientists use an instrument called a spectrometer to study these invisible parts of the rainbow. The atmosphere opposite a rainbow, facing the sun, is often glowing. This glow appears when rain or drizzle is falling between the viewer and the sun. The glow is formed by light passing through raindrops, not reflected by them. Some scientists call this glow a zero-order glow.

Sometimes, a viewer may see a "double rainbow. Double rainbows are caused by light being reflected twice inside the raindrop. As a result of this second reflection, the spectrum of the secondary rainbow is reversed: red is on the inner section of the arch, while violet is on the outside. Light can be reflected from many angles inside the raindrop. A rainbow's "order" is its reflective number. Primary rainbows are first-order rainbows, while secondary rainbows are second-order rainbows.

Higher-order rainbows appear to viewers facing both toward and away from the sun. A tertiary rainbow, for example, appears to a viewer facing the sun. Tertiary rainbows are third-order rainbows—the third reflection of light.

Their spectrum is the same as the primary rainbow. Tertiary rainbows are difficult to see for three main reasons. First, the viewer is looking toward the sun—the center of a tertiary rainbow is not the antisolar point, it's the sun itself.

Second, tertiary rainbows are much, much fainter than primary or secondary rainbows. Finally, tertiary rainbows are much, much broader than primary and secondary rainbows. Quaternary rainbows are fourth-order rainbows, and also appear to viewers facing the sun. They are even fainter and broader than tertiary rainbows. Beyond quaternary rainbows, higher-order rainbows are named by their reflective number, or order.

In the lab, scientists have detected a th-order rainbow. A twinned rainbow is two distinct rainbows produced from a single endpoint. Twinned rainbows are the result of light hitting an air mass with different sizes and shapes of water droplets—usually a raincloud with different sizes and shapes of raindrops.