Rainbow

Double rainbow and supernumerary rainbows on the inside of the primary arc. The shadow of the photographer's head on the bottom marks the centre of the rainbow circle (antisolar point).

Droplets in the Earth's atmosphere as a result of the spectrum of the rainbow appear in the sky, the light, which is caused by the reflection of light from an optical and meteorological phenomenon. It takes the form of multi-colored arc.
Caused by sunlight always a rainbow appears in the section of the sun across the sky.

from inside the arc in the "rainbow" primarary red and purple outer part is displayed. When you leave, and following on the back of the droplet internal reflected rainbow is caused by light that is refracted again while entering the water droplet refractive

Double rainbow outside the primary arc, second arc can be seen that the order of the colors in a rainbow pointing towards the other red one was reversed. The second droplets inside the double rainbow is caused by reflected light.

Rainbows can form in mist, such as that of a waterfall

Rainbow with a faint reflected rainbow in the lake

Rainbow after sunlight bursts through after an intense shower in Maraetai, New Zealand

Circular rainbow seen while skydiving over Rochelle, Illinois

Number of colours in spectrum or rainbow

Spectra obtained using a point source and a glass prism, is a continuation of the wavelength band. The number of colors that the human eye can be distinguished in this spectrum is of the order of 100. Thus, the Munsell color system (on the same stage on the human visual perception system of the 20th century, the numeric description for color) 100 colors are separated. However, the human brain tends to divide them into a small number of basic colors to merit. The apparent discreteness of the default color is the stuff of the human brain. Red, yellow, green, blue and purple: Newton originally (1672) the five basic color spectrum is divided. Is later likened to the notes of the musical scale to the number of seven primary colors, with orange dye. Munsell color system, remove the orange and dye again returned to the five basic colors. Somewhat arbitrary choice of the exact number of the primary color on human will.