Rainbows are caused by a phenomenon known as refraction, dispersion, and reflection of light. When sunlight enters a raindrop, the light is refracted, bending as it passes from air to water. As light travels through the droplet, it is dispersed into its component colors—red, orange, yellow, green, blue, indigo, and violet. This dispersion occurs because different colors of light bend at slightly different angles. When the light exits the droplet, it is refracted again, resulting in the circular arc of a rainbow. The best time to observe rainbows is when sunlight shines during or just after rain.