With reference to the Earth's atmosphere, which one of the following statements is correct?
Show answer
Answer: C. Water vapour, concentrated in the lower atmosphere, absorbs much of the infrared (heat) radiation. That is why humid air traps heat and water vapour is a key greenhouse gas.
Watch for: Infrared does form a large share of sunlight, which makes option B sound plausible.
Why the other options are wrong
- A. Wrong because the equator gets only about 2 to 3 times the annual insolation of the poles, not 10 times.
- B. Wrong because infrared is roughly half of solar radiation, not two-thirds.
- D. Wrong because infrared is outside the visible spectrum.
Source to check: NCERT Class 11 Fundamentals of Physical Geography, Ch 8 Solar Radiation, Heat Balance and Temperature, and Ch 7 Composition and Structure of Atmosphere
Answer from the official UPSC key. Written and fact-checked by AI against the official key. Spotted a mistake? Report it.