Question

What is the order of colours in a rainbow, from the outside to the inside?

Answer 1

Light is a type of electromagnetic wave. Light contains various electromagnetic waves on the basis of their varying wavelengths. The electromagnetic waves which are visible to the human eye are known as visible spectrum.

Complete answer:
Light is a type of electromagnetic wave. Which means that it has both, an oscillating electric as well as magnetic field. Electromagnetic property of light enables it to travel through vacuum since none of the electric or magnetic fields need a medium to propagate.
When different types of electromagnetic waves are arranged in the order of increasing wavelengths, the order is known as an electromagnetic spectrum. The whole electromagnetic spectrum is not visible to the human eye. The narrow band of wavelengths which is visible to the human eye is known as the visible spectrum. White light is made up of the visible spectrum.
When the white light passes through a prism, it splits into its constituting wavelengths namely, Violet, Indigo, Blue, Green, Yellow, Orange and Red, with Violet having the minimum wavelength and Red having the maximum. This phenomenon is known as dispersion of light.
Rainbows usually occur right after a rainfall. In this case the water droplets which are suspended in the air act as a prism and are responsible for dispersion of light.
The light enters through one surface of the droplet, getting split into its constituent colours. Then it gets reflected from the opposite surface flipping the order of colours and then exits from the same surface. Because of this series of events the order of colours in a rainbow from the outside to the inside is Red, Orange, Yellow, Green, Blue, Indigo and Violet.

Note: The phenomenon of rainbow becomes possible because of three properties of light, Reflection, Refraction and Dispersion. Dispersion is a property which happens because electromagnetic waves of different wavelengths travel with different velocities in a denser medium, and because of different velocities different wavelengths get split up.