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Q63 (NDA-II/2013) Geography › World Physical Geography › Atmospheric structure Answer Verified

Which of the following statements is/are correct? 1. Air close to the Earth’s surface heavier. 2. Air close to the Earth’s surface contains larger quantity of water vapoor and dust particles Select the correct answer using the code given below :

Result
Your answer: —  ·  Correct: C
Explanation

Both statements are correct. Air density and pressure are highest near the Earth's surface and decrease with increasing altitude [6]. Gravity pulls the atmosphere toward the surface, making the air 'heavier' or more dense at lower levels [6]. Regarding the second statement, water vapour is a variable gas that is primarily concentrated in the lower atmosphere and decreases rapidly with height [2]. Similarly, solid particles such as dust, smoke, and sea salts are generally concentrated in the lower layers of the atmosphere due to their weight and proximity to surface sources, although convection can occasionally transport them higher [4]. Absolute humidity, which measures the weight of water vapour per unit volume, also varies across the surface but remains significantly higher at ground level compared to the upper atmosphere [5]. Therefore, the air close to the surface is both denser and contains more moisture and particulates.

Sources

  1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Vertical Variation of Atmospheric Pressure > p. 305
  2. [6] https://en.wikipedia.org/wiki/Density_of_air
  3. [5] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 24: Hydrological Cycle (Water Cycle) > Absolute Humidity > p. 326
  4. [2] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > Water Vapour > p. 64
  5. [4] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > Dust Particles > p. 65
  6. [3] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 10: Water in the Atmosphere > CHAPTER > p. 86
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