A rainbow is an optical and meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun.
Rainbows can be full circles, however, the average observer sees only an arc formed by illuminated droplets above the ground,[1] and centred on a line from the sun to the observer's eye.