(i) Scattering of light - Phenomenon of spreading of light (diffused, reflection) by minute particles in a medium.
(ii) The sky appears blue because of the blue color of sunlight scatter much more strongly than the red colour by particles in atmosphere/ air due to its shorter wavelength.
(iii) At sun-rise and sun-set most of the blue light and shorter wavelengths are scattered away by the particles in the atmosphere as the light from the sun near the horizon passes through thick layers of air and larger distance. The light that reaches us is of a longer wavelength (red colour) giving a reddish appearance.
