what is a rainbow

A rainbow is an optical phenomenon that occurs when sunlight interacts with water droplets in the atmosphere. It forms a multicolored circular arc in the sky, visible opposite to the Sun. Rainbows show a spectrum of colors from red on the outer edge to violet on the inner edge, caused by the refraction, internal reflection, and dispersion of light within water droplets. A primary rainbow is created when sunlight enters a water droplet, bends (refracts), reflects off the back of the droplet, and refracts again as it exits, separating into different colors by wavelength. Sometimes, a secondary, fainter rainbow appears outside the primary arc with reversed color order due to light reflecting twice inside the droplets. Rainbows can also form through other airborne water like mist or spray and may appear after rain when sunlight shines from behind the observer.