UPSC CSE Prelims

Correct Option: B Explanation: Dew requires the ground to lose infrared heat on a clear night until nearby air reaches its dew point. Clouds absorb and re-emit terrestrial infrared radiation downwards, limiting cooling. Option-wise Analysis: A (Incorrect): Clouds absorb outgoing radiation but the important effect is also re-radiation toward the surface. B (Correct): Downward long-wave radiation from clouds keeps the surface relatively warm. C (Incorrect): A cool surface encourages dew rather than preventing it. D (Incorrect): Wind deflection is not the mechanism that suppresses dew on cloudy nights.