| (i) Why does the sky appear blue? |
| (ii) Explain by giving reason, why the sun looks reddish at sunrise and sunset. |
Answer:
(i) Blue colour of sky is due to scattering of sunlight by air molecules. According to Rayleigh?s law, intensity of scattered light, \[I\propto \frac{1}{{{\lambda }^{4}}}.\]So, blue light of shorter wavelength is scattered much more than the red light of larger wavelength. The blue component is proportionally more in light coming from different parts of the sky. That is why sky appears blue. (ii) During sunrise or sunset, the sun is near the horizon. Sunlight has to travel a greater distance. So, shorter waves of blue region are scattered away by the atmosphere. Red waves of longer wavelength are least scattered and reach the observer. So, sun appears red.
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