Q. The blue colour of the clear sky is due to 

Explanation by: Admin

The blue color of the clear sky is due to Rayleigh scattering (a form of diffraction), which occurs when sunlight passes through the Earth's atmosphere. Shorter wavelengths of light (blue and violet) are scattered more than longer wavelengths (red, yellow, etc.). Since our eyes are more sensitive to blue light, the sky appears blue.
Other Options Explained:
(B) Dispersion of light → Dispersion refers to the separation of light into its constituent colors (like when light passes through a prism), but this doesn't explain the color of the sky.
(C) Reflection of light → Reflection involves light bouncing off a surface, not the scattering in the atmosphere.
(D) Refraction of light → Refraction is the bending of light when it passes from one medium to another, which is not the reason for the sky's blue color.
Thus, the correct answer is (A) Diffraction of light.