A rainbow is a spectrum of light formed when sunlight interacts with droplets. Upon entering a water droplet, the white light is refracted, and dispersed, that is, spread apart into its individual wavelengths, just as in a prism. The light inside the droplet then reflects against the back of the water droplet before it refracts and disperses as it exits the droplet. The angle between entering and leaving is 40° for blue light, 42° for red.