give an appropriate explanation

The molecules of air and other fine particles in the atmosphere have size

smaller than the wavelength of visible light. These are more effective in

scattering light of shorter wavelengths at the blue end than light of longer

wavelengths at the red end. The red light has a wavelength about 1.8

times greater than blue light. Thus, when sunlight passes through the

atmosphere, the fine particles in air scatter the blue colour (shorter

wavelengths) more strongly than red. The scattered blue light enters

our eyes. If the earth had no atmosphere, there would not have been

any scattering. Then, the sky would have looked dark. The sky appears

dark to passengers flying at very high altitudes, as scattering is not

prominent at such heights.