The natural phenomenon that causes rainbows is the refraction, dispersion, and reflection of sunlight in water droplets. When sunlight enters a raindrop, it slows down and bends, which is called refraction. The light then splits into its various colors—red, orange, yellow, green, blue, indigo, and violet—due to the different wavelengths of colors bending by different amounts. After dispersing, the light reflects off the back of the droplet and exits, bending again as it leaves the droplet. The combined effects create the circular arc of colors we perceive as a rainbow, typically visible when rain is falling in one part of the sky while the sun shines in another.