Rainbows are formed by the refraction, dispersion, and reflection of sunlight in water droplets in the atmosphere. The process involves the following key steps:
Sunlight Entering Raindrops:
Rainbows are most commonly observed when sunlight passes through raindrops in the atmosphere. The sunlight is made up of various colors, which we perceive as white light.
Refraction of Light:
As sunlight enters a raindrop, it undergoes refraction. Refraction is the bending of light as it passes from one medium (air) to another (water). The different colors of light are refracted by different amounts because of their varying wavelengths.
Dispersion of Light:
The refraction of light in raindrops causes the different colors to spread out or disperse. This separation of colors is known as dispersion.
Internal Reflection:
After dispersion, the light undergoes internal reflection within the raindrop. Some of the light reflects off the inside surface of the raindrop.
Refraction Again:
After internal reflection, the light exits the raindrop and undergoes refraction again. This refraction as the light exits the raindrop contributes to the bending of the light.
Formation of a Circular Arc:
The combination of refraction, dispersion, and internal reflection results in the formation of a circular arc of colors in the sky. This arc is what we see as a rainbow.
Color Sequence:
The sequence of colors in a rainbow, typically observed in the order red, orange, yellow, green, blue, indigo, and violet (ROYGBIV), is a result of the dispersion of light. Each color corresponds to a specific wavelength of light.
Double Rainbows:
Sometimes, a second, fainter rainbow (called a secondary or double rainbow) is observed outside the primary one. The colors in the secondary rainbow appear in the reverse order.
It’s important to note that the visibility of a rainbow depends on specific conditions, including the angle of the sunlight, the observer’s position, and the presence of rain or water droplets in the air. Rainbows are not physical objects but rather optical and meteorological phenomena created by the interaction of sunlight and water droplets.