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Q12 (IAS/2024) Geography › World Physical Geography › Atmosphere composition Official Key

With reference to "water vapour", which of the following statements is/are correct ? 1. It is a gas, the amount of which decreases with altitude. 2. Its percentage is maximum at the poles. Select the answer using the code given below :

Result
Your answer: —  ·  Correct: A
Explanation

The correct answer is option A (1 only).

**Statement 1 is correct:** Water vapour is a variable gas in the atmosphere, which decreases with altitude.[1] Additionally, 90% of moisture content in the atmosphere exists within 6 km of the surface of the earth.[2] This clearly confirms that the amount of water vapour decreases as we move higher in the atmosphere.

**Statement 2 is incorrect:** In the warm and wet tropics, water vapour may account for four per cent of the air by volume, while in the dry and cold areas of desert and polar regions, it may be less than one per cent of the air. Water vapour also decreases from the equator towards the poles.[1] This demonstrates that water vapour percentage is actually minimum at the poles, not maximum. The maximum concentration occurs in warm, tropical regions where evaporation rates are highest.

Therefore, only statement 1 is correct, making option A the right answer.

Sources
  1. [1] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > Water Vapour > p. 64
  2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Water Vapour > p. 272
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Don’t just practise – reverse-engineer the question. This panel shows where this PYQ came from (books / web), how the examiner broke it into hidden statements, and which nearby micro-concepts you were supposed to learn from it. Treat it like an autopsy of the question: what might have triggered it, which exact lines in the book matter, and what linked ideas you should carry forward to future questions.
Q. With reference to "water vapour", which of the following statements is/are correct ? 1. It is a gas, the amount of which decreases with …
At a glance
Origin: Books + Current Affairs Fairness: Moderate fairness Books / CA: 6.7/10 · 3.3/10
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This is a textbook 'Sitter' directly from NCERT Class XI Physical Geography. It penalizes aspirants who skim basic chapters like 'Composition of Atmosphere' to rush towards complex climatology. If you missed this, your static foundation has cracks.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Is water vapour the gaseous phase of water in Earth's atmosphere?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Science-Class VII . NCERT(Revised ed 2025) > Chapter 7: Heat Transfer in Nature > 7.4 Water Cycle > p. 98
Presence: 5/5
“You have also learnt in the Grade 6 Science textbook Curiosity, that water exists in three states in nature. As a liquid, it fi lls the oceans, rivers, and lakes on the Earth. As a solid, it forms snow, ice sheets, and glaciers in the mountains and the polar regions. As a gas, it exists in the form of water vapour in the Earth's atmosphere. During summers, some of the snow and ice gets converted to water due to the Sun's radiation and fl ows down as rivers, and ultimately into the oceans. The melted ice is replenished by fresh snow during winters.”
Why this source?
  • Explicitly identifies water vapour as the form in which water exists as a gas in the Earth's atmosphere.
  • Places this gaseous form within the context of the water cycle and the three physical states of water on Earth.
Exploring Society:India and Beyond ,Social Science-Class VII . NCERT(Revised ed 2025) > Chapter 2: Understanding the Weather > Water vapour: > p. 29
Presence: 5/5
“Water vapour is water in gaseous instead of liquid form.”
Why this source?
  • Defines water vapour as water in the gaseous rather than liquid form.
  • Provides a clear, direct definition linking 'water vapour' to the gaseous phase.
FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 10: Water in the Atmosphere > CHAPTER > p. 86
Presence: 5/5
“Y ou have already learnt that the air contains water vapour. It varies from zero to four per cent by volume of the atmosphere and plays an important role in the weather phenomena. Water is present in the atmosphere in three forms namely – gaseous, liquid and solid. The moisture in the atmosphere is derived from water bodies through evaporation and from plants through transpiration. Thus, there is a continuous exchange of water between the atmosphere, the oceans and the continents through the processes of evaporation, transpiration, condensation and precipitation. Water vapour present in the air is known as humidity.”
Why this source?
  • States that water in the atmosphere occurs in three forms, explicitly including the gaseous form.
  • Links atmospheric moisture and the term 'water vapour' to the gaseous state of water (humidity).
Statement analysis

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Statement analysis

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