With reference to the Earth's atmosphere, which one of the following statements is correct?
Answer & explanation
Answer: (c) Infrared waves are largely absorbed by water vapour that is concentrated in the lower atmosphere.
Statement (c) is correct: water vapour, ozone and other gases in the lower atmosphere (the troposphere) absorb much of the near-infrared radiation passing through. The other options misstate insolation values or the nature of infrared light.
- ✓ (c) NCERT says water vapour, ozone and other gases within the troposphere absorb much of the near-infrared radiation. Water vapour is concentrated in the lower atmosphere.
- ✗ (a) NCERT gives insolation at the surface as about 320 W/m2 in the tropics and about 70 W/m2 at the poles, a ratio of under five, and it says the equator receives less than the tropics. Ten times is far too high.
- ✗ (d) Infrared waves lie just beyond the visible spectrum; the human eye cannot see them. They are not part of the visible spectrum.
Remember · In the troposphere, water vapour, ozone and other gases absorb much of the near-infrared radiation. Insolation is about 320 W/m2 in the tropics and 70 W/m2 at the poles.
📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 8 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 8 (practise this chapter)
Sources
- NCERT Class 11 · Fundamentals of Physical Geography, Chapter 8 “Within the troposphere water vapour, ozone and other gases absorb much of the near infrared radiation.”
- NCERT Class 11 · Fundamentals of Physical Geography, Chapter 8 “The insolation received at the surface varies from about 320 Watt/m2 in the tropics to about 70 Watt/m2 in the poles.”
- Infrared Waves (NASA Science, Electromagnetic Spectrum) ↗ “the human eye cannot see it, but humans can detect it as heat. A remote control uses light waves just beyond the visible spectrum of light—infrared light waves—to change channels on your TV.”
Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·