Answer:
The Short Answer: A rainbow is caused by sunlight and atmospheric conditions.
Explanation:
Light enters a water droplet, slowing down and bending as it goes from air to denser water. The light reflects off the inside of the droplet, separating into its component wavelengths--or colors. A full rainbow is actually a complete circle, but from the ground we see only part of it. From an airplane, in the right conditions, one can see an entire circular rainbow.
In summary, a light, such as the sun, hits a droplet of water. The light reflects off of the water droplet and causes you to see multiple colors, a rainbow. This is why rainbows happen during rainy days with the sun poking through.
Do rainbows actually move?
No, they do not. Rainbows are an optical effect that results from light refracting through water droplets in the air. The perceived color of the water droplets is determined by the angle between you, the water droplet, and the sun. This is why rainbows seem to float in the sky and move as you walk. Sometimes, you can find the end of the rainbow on the ground.
