Light is deemed to travel through space in the shape of waves. These waves are of different'length, the blue and violet being short, while the red and yellow are long. The blue waves emerging laterally are more completely scattered than the ved or yellow ones. Hence on certain occasions, the greater part of the sky appears blue. On a hazy day, the blue rays are less, and the. sky appears whitish. Near the horizon, the sky is whiter than at the zenith. Sunset "colours are reddish, because the rays reaching us directly have lost. much of their blue through
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