The colorful, unending circles result from the reflection and refraction of sunlight when it strikes a raindrop.
- The phenomenons of reflection and refraction, both involve a change in the direction of waves and are therefore capable of creating optical illusions like rainbows.
- Yes, rainbows don’t exist in the sky, their appearance is largely determined by the position of the sun and the viewer.
- To a person on the ground, it is visible as an arc while a viewer from the aircraft can see the complete circles wrapped in colors. The part above the horizon is visible from the ground.
- The center of these colorful circles is the antisolar point which can be defined as an imaginary point that lies opposite to the sun.
Sunlight, as perceived by the human eye is white. When this light strikes the raindrop, some part is reflected and some part is refracted. The refracted ray of light undergoes reflection within the raindrop at different angles. These multiple reflections at different angles cause the wavelengths of the spectrum to split and produce colors. The red color having the longest wavelength is present on the outer end of the arch while the violet color has the shortest wavelength and stands at the inner end. The colors overlap at the edges producing a sheen of white light that is present inside the rainbow.
The zero-order glow
Have you noticed the atmosphere opposite to a rainbow? It is usually glowing. This glow is formed by the unreflected light rays that pass through the water drops. This glow has been termed as the zero-order glow by scientists.
The radius of the rainbow
The radius of the rainbow depends on the refractive index of the water droplet. Refractive index can be taken as a measure of the bending of rays. The higher the refractive index, the smaller the radius of the bow. This is the reason why the rainbows formed by sea spray are smaller than the ones resulting from freshwater. The refractive index of saltwater is higher than freshwater.
Light is reflected at many angles within a raindrop. The order of a raindrop is its reflective number. The number of reflections within the raindrop determines the number of rainbows formed.
- When the light is reflected twice in the raindrop, a faint secondary rainbow appears above the primary one. This double reflection causes the spectrum of the secondary rainbow to be reversed. In this case, the outer part of the arch is violet while the inner arch is red.
- The secondary and tertiary order rainbows are quite faint and centered around the sun. Therefore they aren’t visible to the viewer. The fourth-order rainbow is even broader than the tertiary one.
- There are rainbows beyond the quaternary order too. A 200th order rainbow has also been discovered by scientists.
When light hits a rain cloud with different raindrops’ sizes, a twinned rainbow is formed. Twinned rainbows are produced from a single endpoint.
When the cloud has almost similar-sized raindrops, a supernumerary rainbow is formed. It is visible as a thin, pastel-colored arc. In this type of rainbow, the rays interact in interferences that may be constructive or destructive. When a primary rainbow is reflected by a water body, a reflection rainbow is formed.
A reflected rainbow appears on the surface of the water body. During sunrise and sunset, light travels further in the atmosphere. The shorter wavelength lights are scattered all around while the longer wavelength color- red, is visible in the red rainbow or monochrome. The red rainbow thus appears at sunrise or sunset.
When the light strikes fog, the rays are reflected and refracted through the suspended water droplets and a faint rainbow is formed. Since it is formed amid fog, it is called a fogbow and the one that is formed amid clouds is a cloud bow.
Have you heard about the moonbow?
Moonbow is a lunar rainbow that is formed by the light reflected by the moon. Since the moon lacks any light of its own, the moonbow or lunar rainbow has a faint appearance.
A rainbow for peace and a rainbow for diversity
The Buddhist flag of the nineteenth century depicts several aspects of Buddhism like kindness, moderation, blessings, and wisdom through the colors of a rainbow. The vertical arrangement of the bands features the flag. The LGBT pride flag represents the diverse community and the different aspects associated with the colors. Wiphala, the official flag of Bolivia, bears a rainbow.
And no one found the gold
There is an Irish legend that goes by the myth that the end of a rainbow holds a golden pot that is guarded by a tricky leprechaun, but no one can find the gold because the rainbow isn’t the same for all and they don’t end!