(a) The blusih colour predominates in clear sky .
(b) Voilet colour is seen at the bottom of the spectrum when white light is dispersed by a prism. State resons to explain these observations.

Explanation

(a) Blue colour of sky is due to scattering of sunligh. As blue colour has a shorter wavelength than.
(b) When a white light is dispersed by a prism, the violet colour deviates through maximum angle. Hence, it is seen at the bottom of the spectrum.