21. Reason behind advance sunrise and delayed sunset
22. Refraction of light by the earth's atmosphere due to variation in air density is called
23. Select the colours in the correct ascending of wavelength:
24. Sunlight passes through a canopy of a dense forest is due to
25. The air layer of atmosphere whose temperature is less than the hot layer behave as optically
26. The blue colour of the sky is because
27. The bluish colour of water in deep sea is due to
28. The clear sky appears blue because
29. The colour of a star is an indication of its
30. The colour of sky appears blue, it is due to the
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