An eight year old was asked, 'What do you think is a cation?'

Her quick reply was a positively charged kitten.

Why is the sky so blue?

Have you ever tried asking this question why the sky is blue in colour to your teacher? It is interesting to know what renders the blue colour to the vast sky. Definitely there is an answer to such questions. Let us find out the answer right away.

Everyday Chemistry - Why is the sky so blue?

Right from childhood, our teachers have drilled the fact that the sky is blue in colour into our heads. But do you know what renders the blue colour to the sky? Let us find out the answer right away.

What is colour?

Let us first understand how we perceive colours. Colours are just properties of certain objects. Every matter contains molecule of different configurations. When light hits the object, it gets affected by the material and gets scattered everywhere because of the presence of the molecules. The light thus emitted has some colour to it and our eyes perceive them as a particular colour.

How did sky get its colour?

The earth is also an object. It has an atmosphere with gaseous substances like oxygen and nitrogen. When light from the sun hits earth, the molecules of oxygen and nitrogen scatter in all direction. The light from the sun contains several colours like violet, red, orange and yellow. The colour depends on the wavelength of the radiation. The scattering of the molecules also depends on the wavelength, the longer the wavelength the longer the scattering is and vice versa.

Our human eye senses three primary colours, red, green and blue. The blue component is almost ten times stronger than red and violet. Hence even as the earth's component contains red and violet, the human eye views it as blue. When we view the sky away from the sun it appears blue in colour. This is true only on clear sky days. Sometimes when the light emitted by the sun has more of red then we get an orange looking sky. This is true during sunrise or sunset. On days when there are extra particles in the earth's atmosphere like haze, the sky does not seem blue to us.

So the next time you colour sky in your drawings, feel free to colour it orange!

Tags :     Sky     Oxygen     Colours     Molecule     Configurations     Light     Gaseous     Oxygen     Nitrogen     Wavelength     Radiation    

Save a PDF and you save a tree! Try not to take a print of me!

Like Chemistry? Like us!
Also on: