Rainbows are one of nature's most spectacular displays. They appear when sunlight and rain combine in just the right way. The sun shines from behind you while rain falls in front of you, creating the perfect conditions for this colorful arc to appear in the sky.
Sunlight may look white, but it's actually made up of all the colors of the rainbow. This was first demonstrated by Isaac Newton using a glass prism. When white light enters the prism, it bends and separates into its component colors, revealing the hidden spectrum within.
Inside a water droplet, light follows a specific path. First, the white light refracts as it enters the droplet, bending toward the center. Then it reflects off the back surface of the droplet. Finally, as it exits, the light refracts again and disperses into its component colors, creating the rainbow effect.
Rainbows don't appear randomly. They require very specific conditions. The sun must be behind you, shining on water droplets in front of you. The sun's angle above the horizon must be less than 42 degrees. This is why rainbows are most commonly seen in the late afternoon when the sun is lower in the sky.