Why A Rainbow Have Different Colours?

One of the most beautiful phenomena of nature is the formation of rainbow in the sky. Rainbow is usually formed in the shape of an arc consisting of different colors. The colors in the rainbow arc are seven in number starting from Violet in the lower end to the red in the upper end with Indigo, Green, Yellow and orange in between (from Violet to Indigo making the word VIB-GY-OR, the word created to remember the name and arrangement of the colors). In the electromagnetic spectrum, different ranges of frequencies are grouped into what are called frequency bands. One of these frequency bands is called the visible region. Scientifically white light is said to be composed of these seven colors and thus contains all the frequencies of the visible region in it. The phenomenon of formation of rainbow falls in the field of optics. If you place a prism in the dark room and make a ray of light to fall on it with a screen placed at the opposite side of the prism. You will see a band of different colors on the screen which is called spectrum of light. The same law of optics is involved naturally in the formation of rainbow. After the rainfall some water droplets remain suspended in the atmosphere. When sunlight falls or passes through these droplets at low altitude or angle. The light is dispersed into several colors with the water droplets acting as a prism. A rainbow is thus said to be formed making the shape of the arc. The rainbow can more often be seen when sun is at the low elevation and is shining at the back of the observer. The rainbow effect is also commonly seen near waterfalls or fountains because the concentration of water droplets is higher in the nearby region. So from the above discussion we can say that white light means the sunlight is mixture of different colors and the water droplets act as filter, which breaks it to turn into rays of different colors and thus forms a rainbow.

Sunlight is a mixture of light of different wavelengths. Although we can see each as a separate colors, combined they appear to be white. As a ray of sunlight enters a raindrop, its color components are bent, or refracted at different angles and reflected off the raindrop's inner surface. Then as it leaves the rain drop, the light is bent once again. Red, the longest wavelength is reflected to the highest or outer most arcs; violet, the shortest wavelength, to the lowest or innermost arc; violet, the shortest wavelength, to the lows or innermost arc, yellow and green, two arcs between the two. However, a photograph of a lunar rainbow, taken at the correct exposure will be in full color.

Because refraction from sunlight with raindrop

Because of light spectrum