Detailed Explanation:

Answer: Option 3 — Infrared waves are largely absorbed by water vapour that is concentrated in the lower atmosphere.

Water vapour, being a major greenhouse gas concentrated in the troposphere (lower atmosphere), effectively absorbs infrared radiation emitted by the Earth's surface. This absorption is crucial for the greenhouse effect and temperature regulation on Earth.

❌ Option 1 – Incorrect: The equator receives approximately 2.5 times more insolation than the poles, not 10 times. The difference is due to the angle of incidence and Earth's curvature.

❌ Option 2 – Incorrect: Visible light constitutes about 44% of insolation, infrared about 49%, and ultraviolet about 7%. Infrared does not constitute two-thirds of insolation.

✅ Option 3 – Correct: Water vapour in the lower atmosphere (troposphere) is the primary absorber of infrared radiation, making this the correct statement.

❌ Option 4 – Incorrect: Infrared waves have wavelengths longer than visible light (700 nm to 1 mm) and are not part of the visible spectrum (380-700 nm).

📝 Short Notes: Solar Radiation and Atmosphere

• Insolation Composition: Ultraviolet rays (7%), Visible light (44%), Infrared rays (49%)
• Atmospheric Absorption: Ozone absorbs most UV radiation in the stratosphere; water vapour and CO₂ absorb infrared radiation in the troposphere
• Latitude Variation: Equatorial regions receive 2-2.5 times more insolation than polar regions due to angle of incidence
• Greenhouse Gases: Water vapour (most significant), CO₂, methane, and ozone absorb outgoing terrestrial infrared radiation
• Electromagnetic Spectrum: Visible light (380-700 nm), Infrared (700 nm-1 mm), shorter wavelengths have higher energy