Question

The blue colour of sky is due to

• A. scattering
• B. absorption
• C. reflection
• D. diffraction

Answer 1

Answer: (A)

The blue appearance of sky is due to scattering of sunlight from the atmosphere when one looks up at the sky, it is the scattered light that is entering the eyes. Among the shorter wavelengths the colour blue is present in larger proportion in sunlight. From Rayleigh's criteria of scattering $\propto \frac{1}{(wavelength{)}^4}$ light of short wavelength are strongly scattered by the air molecules and reach the observer. This explains the blue colour of sky.