A rainbow is a meteorological phenomenal which has awed humanity with its beauty throughout history. A rainbow is formed as light traveling through the atmosphere interacts with water droplets where refraction, dispersion, and reflection of the light from the droplets leads to the formation of a spectrum of colors in the atmosphere. In theory, rainbows appear as full-circles but are usually seen as an arc. There are numerous types of rainbows which undergo different processes in their formation.
9. Twinned Rainbow
Twinned rainbows are some of the rarest types of rainbows to occur in nature. These rainbows start from a common base but split along the arc making a primary rainbow and a secondary rainbow with the two having colors appearing in the same order. The color profile in twinned rainbows is the same spectrum as that in a regular rainbow. 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 millimeters and 0.45 millimeters with the small variation in size being the cause of the splitting of the rainbow into two. In some instances, the rainbow can even split into three branches, but such occurrences are extremely rare.
8. Multiple Rainbows
Multiple rainbows are another type of rainbow which is also a rare occurrence. Multiple rainbows are sometimes referred to as double rainbows. As the name suggests, multiple rainbows are instances when more than one rainbow occur simultaneously in the same place and are made up of a primary rainbow and other secondary rainbows. The region in-between the multiple rainbows which is unlit is officially known as Alexander’s band, named after Alexander of Aphrodisias, a 2nd-century Peripatetic philosopher who first described the band. Multiple 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 colored bands of the rainbows.
7. Full-circle Rainbow
With the right conditions, all rainbows are supposed to form a full-circle as opposed to the semi-circular shape usual seen. However, several limitations brought about by the sun’s position in the sky or obstructions of the sun by the landscape prevent the observation of a rainbow in its full-circle. These limitations can be removed by moving to high altitudes such as at the top of a tall building or on board an airplane, and a full-circle rainbow can be observed. In rare cases, full-circle rainbows can be made up of a primary bow and a secondary bow. Full-circle rainbows can also be formed artificially by spraying water mists through a hose when facing away from sunlight.
6. Supernumerary Rainbows
Another rare type of rainbow is the supernumerary rainbow. This rainbow appears as an extra band inside the primary rainbow 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, usually having a diameter not exceeding 1 millimeter. One distinct feature of supernumerary rainbows is that they are made up of pastel colors instead of the normal spectrum present in the usual rainbow.
5. Monochrome Rainbow
A monochrome rainbow is a type of rainbow whose color spectrum is based on a single color, usually red. Also known as a red rainbow, a monochrome rainbow 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 color. A monochrome rainbow has quite a dramatic effect on the atmosphere.
4. Reflected Rainbow and Reflection Rainbow
A reflected rainbow and a reflection rainbow are two distinct types of rainbows, but both 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.
3. 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.
2. Rainbows Under Moonlight
Rainbows are thought of being a result of the reflection and deflection of sunlight on water droplets. However, in some instances, rainbows can also be formed under moonlight, but such instances are extremely rare. Nonetheless, on the few occasions when rainbows under moonlight are formed during a full moon or a near equivalent. These rainbows which are also known as moonbows are thought to display a single color but are made up of a spectrum of different colors, but due to the dullness of moonlight in comparison to sunlight, these colors are not visible to the naked human eye.
A fogbow is a special type of rainbow which is formed as sunlight travels through a small cloud or fog and the fog droplets diffract the sunlight. The color spectrum in a fogbow is usually white, red and blue. Fogbows are usually formed over a body of water or in an area with thin fog.