UPSC Prelims 2023 · Question 72 of 97
UPSC Prelims 2023 question on Atmosphere Infrared Absorption
- ExamUPSC CSE
- Year2023
- PaperGeneral Studies Paper I
- SubjectGeography
- TopicClimatology
- DifficultyMedium
- TypeDirect
With reference to the Earth's atmosphere, which one of the following statements is correct?
Show answer
Answer: C. Infrared waves are largely absorbed by water vapour that is concentrated in the lower atmosphere.
Analysis
Hence option (c) is the correct answer.
Statement by statement
Option (a) – INCORRECT: The insolation received at the surface varies from about 320 Watt/m2 in the tropics to about 70 Watt/m2 in the poles. Therefore, the total amount of insolation received at the equator is roughly about 5 times of that received at the poles — not 10 times.
Option (b) – INCORRECT: Insolation is frequently referred to as shortwave radiation; it falls primarily within the ultraviolet and visible portions of the electromagnetic spectrum. Infrared rays do not constitute two-thirds of insolation.
Option (c) – CORRECT: Water vapour is the most abundant greenhouse gas in the Earth's atmosphere, and it has strong absorption properties in the infrared portion of the electromagnetic spectrum. As infrared radiation passes through the atmosphere, water vapor molecules can absorb and re-emit a significant portion of the longwave radiation. The atmosphere is largely transparent to shortwave solar radiation. Within the troposphere, water vapor, ozone and other gases absorb much of the near infrared radiation.
Option (d) – INCORRECT: Infrared waves are NOT part of the visible spectrum of electromagnetic waves in solar radiation. The visible spectrum refers to electromagnetic waves visible to the human eye, with wavelengths between approximately 400 to 700 nanometers. Infrared waves have wavelengths longer than approximately 700 nanometers.