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UPSC Prelims 2019 Paper-1 📅 02 Jun, 2019

Why are dewdrops not formed on a cloudy night?

A
Clouds absorb the radiation released from the Earth's surface.
B
Clouds reflect back the Earth's radiation.
C
The Earth's surface would have low temperature on cloudy nights.
D
Clouds deflect the blowing wind to ground level.
Result Summary
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UPSC Prelims
2019 • 02 Jun, 2019 • Paper-1
Why are dewdrops not formed on a cloudy night?
Correct Answer
Clouds reflect back the Earth's radiation.
Dew Formation Physics: Dew forms on clear, calm nights when the Earth's surface rapidly loses heat through outgoing longwave terrestrial radiation, causing the ......
Ref/Book : UPSC Prelims 2019
Ref. Subject Geography
Chapter -
Ref. Topic Climatology
Pg. No -
💡 Analysis & Explanation
Dew Formation Physics ▼
Dew forms on clear, calm nights when the Earth's surface rapidly loses heat through outgoing longwave terrestrial radiation, causing the surface temperature to drop below the dew point and condensing atmospheric moisture.
Cloud Cover Interference ▼
On a cloudy night, the thick layer of clouds acts like a blanket. It intercepts the outgoing longwave radiation from the Earth and reflects/re-radiates it back to the surface. This prevents the ground from cooling down sufficiently to reach the dew point, thereby preventing condensation.
Conclusion ▼
The reflection of terrestrial radiation by clouds halts the necessary cooling process, matching option B.
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