The sky appears blue because of
(1) Atmospheric water vapour
(2) Scattering of light
(3) Reflection on seawater
(4) Emission of blue wavelength by the sun
Answer: (2), The sky is blue because the molecules in the air scatter light in the higher wavelengths (that is, the blue light), while lower wavelength light (that is, the light on the red end of the spectrum) goes through to the ground. So the light that gets finally reflected down from the scattering is blue, therefore a blue sky. This is called Rayleigh scattering. Rayleigh scattering, named after the British physicist Lord Rayleigh, is
the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light. The particles may be individual atoms or molecules. It can occur when light travels through transparent solids and liquids but is most prominently seen in gases.
