Rainbows



Rainbows are a phenomenon that occurs when light is reflected through raindrops in the atmosphere, causing a dispersion of visible white light into light of different wavelengths, or colors. One can see a rainbow if your back is to the sun and you look up at an approximately 42 degree angle in the atmosphere with suspended drops of water, such as mist or rain.

Separation of Colors


When light passes through into a medium with a different density, it can slow down or speed up. When light enters a rain droplet, it decreases in speed, causing a bending of light, or refraction. In a rainbow, light rays from the sun refract into a water droplet, internally reflect, and then refract out of the droplet. This results in a dispersion of light into the eyes of the viewer.

Layers in the Sky


Blue and violet light have shorter wavelengths than red light, resulting in greater refraction than red light. Red light is refracted at a steeper angle to the ground, while blue light is seen at less steep angles. This results in red light always being visible from the top of the rainbow while blue light is seen from the bottom.

Cooler Rainbows


Droplets in a rainbow form a circular arc. When viewed from the ground, viewers only see a half circle, but when viewed from an airplane, viewers can see the rainbow in its entirety, in a full circle.



A double rainbow occurs when a secondary rainbow is present above the primary rainbow. While light rays in the primary rainbow experience one internal reflection, rays in the secondary rainbow go through two internal reflections. Red light exits the drop at a 50 degree angle, while blue light exits at a 53 degree angle, resulting in a secondary rainbow that has a reversal of colors from the primary rainbow.