A rainbow is created when white light is bent (refracted) while entering a droplet of water. The electromagnetic spectrum is made of light with many different wavelengths, and each is reflected back at a different angle therefore producing a rainbow.
A rainbow is actually round like a circle. On the ground, the bottom part is hidden, but in the sky, it can be seen as a circle around the point opposite the sun.
Rainbows often appear after storms and are popular symbols for peace in many cultures.
Previously scientists tried to classify rainbows based on the colours in the rainbows, or the size of the droplets they refracted through but those classifications often missed certain types of rainbows. There are more types of rainbows in the world than you may realize —some rarer than others. Each type of rainbow is created under different circumstances and falls either into primary or secondary types. Here are a few types and descriptions
Fogbow rainbow
A fogbow is a type of rainbow that is formed as sunlight travels through a small cloud or fog and the fog droplets diffract the sunlight. It can also form above any body of water. The predominant colour of a fogbow rainbow is white, with blue appearing on the inside and red appearing at both ends.
Lunar or moonbow rainbow
A lunar or moonbow rainbow occurs on rare occasions when there is a full moon or almost fully lit up When it does, it appears as a white arc lining the moon’s outer rim. but are actually made up of a spectrum of different colours, but due to the dullness of moonlight in comparison to sunlight, these colours are not visible to the naked human eye.
Double or multiple rainbows
Double (or multiple ) rainbows occur when several rainbows form simultaneously in the same place at the same time. They are made up of one primary rainbow as well as several other secondary rainbows. Double rainbows are formed by the double reflection of sunlight inside raindrops and are between 130 degrees and 127 degrees in width. The reflection of white light takes place inside the coloured bands of the rainbows White light reflects off the colours of the primary rainbow, creating secondary ones.
There is always an unlit space in between each rainbow which is known as Alexander’s Band after Alexander of Aphrodisias, a 2nd-century Peripatetic philosopher who first described the band.
Twinned rainbows
Twinned rainbows start from a common base but split along the arc making a primary rainbow and a secondary rainbow with the two having colours appearing in the same order. Twinned rainbows are formed when the light is refracted after coming across two rain showers which have distinct sizes of raindrops. The sizes of raindrops in the two rain showers are usually 0.40 mm and 0.45 mm with the small variation in size being the cause of the splitting of the rainbow into two. In some rare instances, the rainbow can even split into three branches. The colour profile in twinned rainbows is the same spectrum as that in a regular rainbow and the colours appear in the same order
Distinction:
A double rainbow is when there are two separate rainbows over the top of each other.
A twin rainbow is when one splits in to two separate bows.
Full Circle
With the right conditions, all rainbows are supposed to form a full-circle as opposed to the semi-circular shape usual seen The rainbows that we usually see are semi-circular but sometimes in high altitude areas it is possible to spot a full circle rainbow. They can also be sometimes seen on the top of a tall building or on board an airplane. When they form, it may include both primary and secondary rainbows. Full-circle rainbows can also be formed artificially by spraying water mists through a hose when facing away from sunlight.
At lower altitudes, the position of the sun prevents a full circle from being formed. Anything obstructing the sun also makes it impossible for this type of rainbow to form.
Supernumerary rainbows
Supernumerary bows are rare but can occur in primary rainbows, acting as another band inside of it or in some cases, outside the secondary rainbow and normally occurs in fogbows. Supernumerary rainbows are detached from the main bow known as the stacker rainbow, and as they move away from the main bow, they become fainter. Supernumerary rainbows are formed as sunlight strikes small droplets of water, with a diameter not exceeding 1 mm.
Unlike 'normal' rainbows, supernumerary rainbows are made up of pastel colours instead of the normal spectrum
Monochrome or red rainbows
A monochrome rainbow is a type of rainbow whose colour spectrum is based on a single colour, usually red. It is a rare meteorological occurrence and only happens when sunlight travels farthest through the earth’s atmosphere, during sunrise or sunset. Due to the great distance, short wavelength lights such as yellow, blue and green are scattered and displaced from the spectrum leaving only the red colour.
Reflected Rainbows and Reflection Rainbows
A reflected rainbow and a reflection rainbow are two distinct types of rainbows, which are closely related.
A reflected rainbow occurs after sunlight is deflected from droplets of rainfall and then reflected from a water body before being viewed by an observer. Reflected rainbows are sometimes visible on the surface of the water below the horizon and can be viewed (albeit partially) in bodies of water as small as puddles.
A reflection rainbow, on the other hand, is formed when sunlight is first reflected off a body of water, then deflected by raindrops before being visible to an observer. Reflection rainbows are rarely visible due to the complexity involved in their formation.
Higher-Order Rainbows
A rainbow order is a characteristic which is used to categorize rainbows into the two basic groups: primary rainbows and secondary rainbows. The main determinant of a rainbow order is the number of reflections of light in water droplets involved in the formation of a rainbow.
Primary rainbows are also known as first-order and are formed from one light reflection, while secondary rainbows, also known as second-order rainbows, are made of two reflections
There are other rainbows which are formed from more than two internal reflections, and these are known as higher-order rainbows. The number of internal reflections is not limited and runs to infinity, but the higher-order rainbows become less visible as the number of internal reflections increase.
Just as a balance to all the technical stuff, and bring us a step back closer towards the awe and wonder aspect of rainbows, here is a link to a selection of songs with a rainbow theme
