^Appearance of sky

The appearance of sky from earth at various locations depend on the amount & nature of impurities present in the air & climatic conditions also.

Also it is found that the light scattered

(a) at right angles to the direction of incidence is completely plane polarized light (CPL)

(b) along the direction of incidence is unpolarized, &

(c) at all other angles to the direction of incidence is partially plane polarized light (PPL)

On the Moon, there is no blue sky because there is no atmosphere & thus no scattering. Even during the day, the sky is as black as at night, although the Sun and the Earth may be brightly shining.

If we look at the blue portion of the sky through a Polaroid and rotate the polariod, the transmitted light shows rise and fall of intensity, which indicates that the light from the blue portion of the sky is plane polarized.