Explain briefly the reason for the blue of the sky.

i. Sky appears blue due to a phenomenon called scattering of light. When a wavelength of certain frequency strikes the atom, the atom absorbs the energy and gets excited to another level.

ii. Excited state is an unstable state, so in order to attain stability, the atoms comes back to the ground state releasing energy in form of light. This process occurs in scattering of light.

iii. Scattering phenomenon occurs only when the size of the atom is comparable to the wavelength of light. Our atmosphere is comprised of oxygen and nitrogen molecules. So the wavelength of blue & violet is comparable to these molecules.

iv. Therefore the molecules present in air scatter the blue & violet light. As human eye is sensitive to blue more than violet, therefore the sky appears blue Also the intensity of light depends on the angle of scattering. Intensity is maximum when angle of scattering is equal to 90 degrees. This is the reason why the sky appears more blue overhead than other parts.