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Science of Colors

Seven colours of 'Rainbow'
During rainy season, what we see in the sky is brilliant 'Rainbow' in a semi circular form with its seven colours. Once the famous scientist and Noble Laureate Richard Feynman looking at a 'Rainbow'. So keenly as if he is witnessing it for the first time in his life time and is not going to see it again. One of his colleagues questioned him "Professor! Why are you looking at that rainbow so keenly? Feynman without turning his head replied". Because, it is 'Beautiful'. Indeed, Rainbow is one of the beautiful scenes which nature has endowed on humanity.

In fact, rainbow forms either before it rains or afterwards opposite to the sun and not during the rain. We all learnt in school that the famous scientist. Isaac Newton found that white coloured sunlight when passed through a glass prism, it splits up into seven of its constituent colours. During rainy season, the moisture in the atmosphere will be in the form of tiny drops of water (rain). These drops settle on the air and dust particles in the atmosphere and will be hanging in the form of a screen or chain.

Due to the earth's gravity, the spherical drops will be little elongated and function as glass prisms.

Now, one of the white light rays of the sun opposite to this chain will travel through one of the water (rain) drops. This ray undergoes 'refraction' and splits up into its seven of its constituent colours Violet (V), Indigo (I), Blue (B), Green (G), Yellow (Y), Orange (O) and Red (R). These seven colours (VIBGYOR) will fall on the layer of the drop on the other side get reflected and turn back. The seven colours which turned back will again undergo refraction while coming out of the raindrop and spread to a greater extent. This process takes place in lakhs of water drops at the same time and all those coloured rays are entering our eyes, the effect of which we see in the form of a 'rainbow'. The 'upper part' of the rainbow will have 'red' colour and the 'lower part' will be 'violet'.

The rainbow will be in the form of a 'bow' and not as' 'arrow' because the hanging chain of water drops in the atmosphere will take the curved shape of the earth because of the gravitational pull of the earth.

Sometimes we see two rainbows at the same time one over the other. When white light ray refracts twice in each water drop, the second rainbow forms. But this will not be as bright as the first one. In this the colours will be in the reverse order to that in the original one.

Even in the floating water drops near water falls we can find a rainbow.
Prof. Laxmi... Emani
Published date : 13 Dec 2012 06:10PM

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