UPSC Prelims 2019 · Question 84 of 99
UPSC Prelims 2019 question on Dew Formation Cloudy Night
- ExamUPSC CSE
- Year2019
- PaperGeneral Studies Paper I
- SubjectGeography
- TopicClimatology
- DifficultyEasy
- TypeDirect
Why are dewdrops not formed on a cloudy night?
Show answer
Answer: B. Clouds reflect back the Earth's radiation.
Verdict
Correct answer: Clouds reflect back the Earth's radiation → Option (b).
Analysis
Dew is not formed on cloudy nights because cloudy nights are warmer than clear nights.
The atmosphere, heated by the absorption of Earth radiation, in turn radiates heat back to the Earth's surface, increasing the Earth's surface temperature. Clouds act as a blanket, reflecting back the Earth's radiation and keeping the surface warmer.
On cloudy nights, this reflected radiation keeps the temperature above the dew point, preventing the formation of dewdrops. On clear nights, the Earth's surface loses heat rapidly to the atmosphere, the temperature drops below the dew point, and dew forms.