How Rainbows Are Made

Rainbows aren’t a physical object, nor do they actually exist.
Rainbow: an optical phenomenon or illusion caused by both light reflection and refraction.
In order for a rainbow to appear, certain conditions must be met. * It needs to have just rained because a rainbow needs the water droplets to float in the air. * The viewer must be standing in front of the sun, and the clouds must be cleared away from the sun. * Whether or not a rainbow appears is heavily dependent on where the viewer is standing and where the sun is

When sunlight shines on the water droplets, it hits them at 42°.
The light slightly refracts as it enters the water droplets because water is denser than air, causing the light to travel slower.
The light is then reflected off of the back of the water droplet, and the reflected light is refracted again at several different angles when it exits the droplet.
The light refracts again when it exits the water droplet because air is less dense than water, causing the light to increase in speed.
In the context of a rainbow, sunlight is considered to be white light.
Sunlight is composed of wavelengths of visible light, some being more bent than others when they enter and exit the water droplets. * The shorter wavelengths generally bend more than the longer wavelengths.
During the second refraction, sunlight separates into all the visible light it’s composed of, thus creating a rainbow. * Violet is seen on the bottom since it has the shortest wavelength, and red is seen on the top since it has the longest wavelength.

A full rainbow takes on the shape of a complete circle, but from the ground viewers can only see an arc. * For a chance to see the full circle, viewers should be in an airplane, given the conditions are right.
Antisolar point: the center of the circle of the rainbow, or an imaginary point exactly opposite the sun.
The water droplets refractive index determines the radius of the rainbow. * The higher the refractive index of the water droplet, the smaller the radius of the rainbow, and the smaller the refractive index of the water droplet, the larger the radius of the rainbow.
At the edges of a rainbow, the colors overlap. This causes the inside of a rainbow to appear brighter than the outside.
Double rainbow: occurs when light is reflected twice inside the water droplets. * The second reflection causes the second rainbow to be in reverse order than the primary rainbow. This means red would be on the bottom and violet would be on the top.

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