We explain what a rainbow is and the types of rainbows there are. How it is formed, why it has seven colors and the places with the most rainbows.
What is a rainbow?
The rainbow is a meteorological phenomenon and appears in the form of an arc of multicolored light by the refraction of sunlight (white light) in raindrops that are suspended in the atmosphere. In its most intense manifestation, the seven colors can be seen: red in the upper or outer part and successively orange, yellow, green, cyan (or turquoise), blue and violet in the lower or inner part.
See also: Color wheel
Types of rainbows
The types of rainbows depend on different atmospheric conditions that influence the way the luminous arc is projected, and the main ones include:
- Primary rainbow It is the best known and usually appears after a storm or in areas of slopes with splashing water, like a waterfall.
- Secondary rainbow Also called a “double rainbow”, it is formed above the primary rainbow, with the colors inverted.
- Supernumerary rainbow It is rare to see and consists of the projection of several faint rainbows simultaneously, a product of the diffraction of sunlight.
- Red rainbow Also known as a “monochrome rainbow,” it forms after rain and during sunrise or sunset, with the sun located very low or near the horizon.
- Circumhorizontal arc Also known as a “fire rainbow,” it appears very rarely and is formed from small water droplets in cirrus clouds, where the spectrum of colors is projected (rather than appearing in the shape of an arc).
- Twin rainbow It is very rare to see and is projected with two arcs that, unlike the secondary rainbow, originate from a single base point and their colors are not inverted.
However, For the scientific environment, the classification of rainbows is even more detailed. A study released in 2015 by the French National Center for Meteorological Research, headed by researcher Jean Ricard, establishes that there are twelve different types of rainbows and that this classification considers the number of visible colors, the projection of multiple arcs and the alteration of the color of the sky between each arch. All of these parameters establish small differences between the types of rainbows that we describe above.
How is a rainbow formed?
The rainbow It is formed by the decomposition of a ray of light that passes through a drop of water suspended in the atmosphere. When a ray of light passes through a surface that divides two spaces of different densities (in this case, the air in the atmosphere and the drop of water), the ray refracts its path, that is, it bends or slightly changes the angle of its path. . It is then reflected (bounced) off one of the faces inside the drop and, upon exiting, the light ray is refracted again.
The rainbow can appear anywhere there is moisture in the air for example, near the spray of a river or sea spray, and with the sun located in a specific position: less than 42º above the horizon. The observer must be positioned facing the water drops and with the Sun behind him.
Why does the rainbow have seven colors?
The light ray that passes through the water drop generates a decomposition of the white light into different wavelengths. These lengths are different from each other and give rise to the different colors of the rainbow. This concept of The “decomposition of light” was demonstrated by Isaac Newton in the 17th century through an experiment with a glass prism that was passed through a ray of sunlight. He found that white light was made up of bands of colors that could be separated and visualized individually (just like the rainbow).
Places with the most rainbows
Among the places where rainbows are most visible, the following stand out:
- Machu Picchu Located in the Andes mountain range, south of Peru, it is an ancient Inca town from the 15th century.
- Victoria Falls Located on the border between Zimbabwe and Zambia, in Africa.
- Iguazu Falls Located on the border between the countries Argentina and Brazil.
- Masai Mara Nature Reserve Located in Kenya, Africa.
- Tatra Mountains National Park Located in the Tatra Mountains, Slovakia.
- Jasper National Park Located in the Rocky Mountains, Canada (declared a World Heritage Site by UNESCO in 1984).
- Norfolk Located in England, it is a city with fine sand beaches.
- Grinell Point Mountain Located in Glacier National Park, in Montana, United States.
- Valley of Flowers National Park Located in the state of Uttaranchal, India (declared a World Heritage Site by UNESCO in 1998)
- Mount Fuji. Located west of Tokyo, Japan It is the highest peak on the island of Honshu, located west of Tokyo, Japan.
References
- “Rainbow: Definition, When it is seen, Refraction and Much more…” in Rainbow Colors.
- “Rainbow” in National Geographic.
- “What is a circumhorizontal arc?” in Very Interesting.
- “Supernumerary Rainbows” in Atoptics.
- «The Rainbow: The natural phenomenon in the teaching of physics» in Spanish Physics Magazine.
- “Rainbow Theory” in Divulgameteo.
