Hello friends, to answer the question that why sky appears blue, first of all let us discuss from where light comes? The answer is obvious that is Sun. But after originating from Sun, does the light directly reaches or straightly reaches earth? The answer is NO.

The light travel in form of waves and it passes through atmosphere surrounding our earth. The meaning of atmosphere is place having atoms or airs. Now the atmosphere has air molecules, dust particles and water droplets. The maximum number of gases present in the atmosphere of earth is oxygen and nitrogen.

As white light from Sun consists of seven colors. Exactly, you are right that is the color of Rainbow that is VIBGYOR. You must have seen the same during experiment with Prism. If not try to do it.

You will see Violet, Indigo, Blue, Green, Yellow, Orange and Red that is VIBGYOR.  

The wavelength of these colors vary from 4000 angstroms to 7000 angstroms. 4000 is of Violet and 7000 is of Red. It means the Violet is the shortest wave or we can say that it has shortest wavelength and Red has longest wavelength.

Now come back to what is the role of air particles consisting mostly of nitrogen and oxygen, dust particles or water droplets in appearing the color of sky blue. The air molecules are smallest in size and these molecules will scatter the shortest color or wavelength of light easily that is violet, indigo and blue. But violet is not so bright color and percentage of violet is very low in sun light also and indigo and blue after scattering mixes and give the bluish color to sky after scattering .

This is also proved by Rayleigh Scattering which shows that scattering is inversely proportional to (wavelength)⁴.  It means lesser the wavelength; more will be the scattering. That is case with blue color.

Therefore, due to the scattering of blue light more by air molecules as they have shorter in size, blue color scattered more and thus sky looks blue in color due to this reason.

But here question arises, then why sky looks reddish or orange during sun set and why cloud looks white? Also does the sky looks blue from other planets? We will discuss these in coming articles. In case of doubt, please post in the comments section. Below is our youtube video regarding why Color of Sky is Blue?