Rainbow

Rainbows are optical phenomena when sunlight spread out into its spectrum of colors and diverted to the eye of the observer by water droplets. It can be caused by other forms of water than rain, including mist, spray, dew, fog, and ice. Moreover, rainbows can have shapes other than a bow (arc), including stripes, circles, or even flames.
The coloured rays of the rainbow are caused by the refraction and internal reflection of light when it enters the water drops, then reflected from the drop's opposite side, and refracted again as it leaves the drop and passes to the observer's eye. Each colour being bent through a slightly different angle depend on its wavelength. The red color has the longest wavelength and reflected with the wider angle, so it appears in the outside layer on the arc.The colours of the arc (from outside to inside) are red, orange, yellow, green, blue, indigo, and violet.