Why is the sky blue?

 

However, when looked from earth's surface, the sky looks to be of different colors; blue, primarily. That's because when the parts of lights from the sun reaches us, it goes through many barriers: molecules, gases, dust particles, more. And this makes all difference in terms of how the sky looks.

 

Generally, the lights from the sun look white. However, in reality, it's the combination of many colors that make up of a rainbow.

 

When light travels through space and to us, it hits earth's atmosphere that makes up of dust and gas molecules.

 

Now dust particles are larger than that of the light's wavelength. So, the light that passes through it (or get bounced into different directions), the reflected light still looks white because it continues to carry the same combination of colors.

 

BUT, gas molecules are much smaller as compared to the wavelength of the light. So, when the light hits gas molecules, some of it gets absorbed and radiated from the other end. Now, while the colors of the light get absorbed remain the same, due to the variation in the frequency, different shades react differently. For instance, blue has high frequencies, so it gets absorbed more often than, say, red, which has lower frequencies. (This process is called Rayleigh Scattering, named after Lord John Rayleigh, a physicist who first described it. And this phenomenon is the reason why the sky is blue.)

 

When lights pass through the atmosphere, a part which has higher frequencies and longer wavelength pass straight through without getting affected by air. (Colours include red, yellow, orange.) On the other, the parts of light that have smaller frequencies and shorter wavelengths (color blue) get absorbed by the gas molecules and get dispersed in different directions across the sky. So, now, whichever direction you see in the sky, it looks blue. However, as you move closer to the horizon, the color gets much paler or white.

 

(Courtesy: TES.com)

 

 

Hope this answers your question.

 

If not, here's a video, explaining why the sky is blue:

 

 

(English)

 

 

(Hindi)