NCERT Solution Class 11 Geography Composition and Structure of Atmosphere

Scroll down for PDF

NCERT Solution for Class 11 Geography for chapter 8 Composition and Structure of Atmosphere

1. Multiple choice question

(i) Which one of the following gases constitutes the major portion of the atmosphere?

(a) Oxygen

(b) Nitrogen

(c) Argon

(d) Carbon dioxide

Answer: (b) Nitrogen

(ii) Atmospheric layer important for human beings is:

(a) Stratosphere
(b) Mesosphere
(c) Troposphere
(d) Ionosphere

(c) Troposphere

(iii) Sea salt, pollen, ash, smoke soot, fine soil — these are associated with:

(a) Gases
(b) Dust particles
(c) Water vapour
(d) Meteors

(b) Dust particles


(iv) Oxygen gas is in negligible quantity at the height of atmosphere:

(a) 90 km
(b) 120 km
(c) 100 km
(d) 150 km

(b) 120 km

(v) Which one of the following gases is transparent to incoming solar radiation and opaque to outgoing terrestrial radiation?

(a) Oxygen
(b) Nitrogen
(c) Helium
(d) Carbon dioxide

Answer: (d) Carbon dioxide

2. Answer the following questions in about 30 words

(i) What do you understand by atmosphere?

Atmosphere is a mixture of different gases and it envelopes the earth all round. It contains life-giving gases like oxygen for humans and animals and carbon dioxide for plants.

(ii) What are the elements of weather and climate?
The main elements of weather and climate are temperature, pressure, winds, humidity, clouds and precipitation.

(iii) Describe the composition of atmosphere.

Answer: The atmosphere is composed of gases, water vapour and dust particles.

(iv) Why is troposphere the most important of all the layers of the atmosphere?

Answer: The troposphere is the lowermost layer of the atmosphere. This layer contains dust particles and water vapour. All types of changes in climate and weather take place in this layer. This is the most important layer for all biological activity.

. Answer the following questions in about 150 words

(i) Describe the composition of the atmosphere.

The atmosphere is composed of a number of gases, water vapour and dust particles. Nitrogen and Oxygen are two main gases, which form over 99% of the total volume of the atmosphere. The other gases are argon, carbon dioxide, neon, helium ozone hydrogen, methane, etc. The following chart gives percentage of permanent gases in the atmosphere:



Water vapour is the most important element of the atmosphere. The average amount of water vapour is nearly 2% of the atmosphere by volume, it may-vary from 4% in the worm and wet tropics to less than 1% in dry and cold areas of deserts and the polar regions.

Dust particles comprise the third major component of the atmosphere. They are derived from different sources and include: sea salts, smoke-soot, fine soil, ash, pollen, dust, etc.

(ii) Draw a suitable diagram for the structure of the atmosphere and label it and describe it.

Answer: Structure of the Atmosphere: The atmosphere consists of different layers with varying density and temperature.


Troposphere: This is the lowermost layer of the atmosphere. Its average height is 16 km, although it is only 10 km at the poles and extends up 18 km at the equator. Temperature decreases with height in this layer, roughly at-the rate of 1°C for 165 metres of ascent. This is known as normal lapse rate.

Stratosphere: It extends up to a height of 50 km. The temperature remains almost constant in its lower portion, up to a height of 20 km.

Mesosphere: It lies above the stratosphere, and extends upto a height of 80 km. The upper limit of mesosphere is known as the mesopause.

Ionosphere: The Ionosphere is located between 80 and 400 km above the mesopause. Temperature here starts increasing with height. It contains electrically charged particles known as ions, and hence, it is known as ionosphere. Radio waves transmitted from the earth are reflected back to the earth by ionosphere.

Exosphere: The exosphere is the outermost layer of the Earth's atmosphere. It starts at an altitude of about 500 km and goes out to about 10,000 km. Temperatures in the Earth’s exosphere remain constant with altitude, averaging about 1500 Km.



Click on the text For more study material for Geography please click here - Geography

Latest NCERT & CBSE News

Read the latest news and announcements from NCERT and CBSE below. Important updates relating to your studies which will help you to keep yourself updated with latest happenings in school level education. Keep yourself updated with all latest news and also read articles from teachers which will help you to improve your studies, increase motivation level and promote faster learning

CBSE Board Introduces Experiential Learning for Student

CBSE Academic Session 2019-20: Board Introduces Experiential Learning for Student: The education sector has grown for some new changes. As per the latest updates the Central Board of Secondary Education has been good in making all the possible efforts to improve...

JEE Entrance Exam 2020 Dates Registration Admit Cards Exam Pattern

JEE Entrance exam is conducted for students who wish to pursue engineering in different subjects or categories like mechanical, CS, etc.. It is officially organized and conducted by NTA. Formerly it was organized by CBSE. It avails seats for students in IITs, NITs, and...

Extension of dates by CBSE for Single Girl Child Merit (SGC) scholarship

CBSE has announced to extend dates for SGC scholarship. Previously the dates to submit the SGC scholarship form were 18 October 2019. Now dates have shifted. For online submission, the last date is 31st October. Whereas date for submission of hard copies of renewal...

CBSE examination board hike the fee for class 10th and 12th

The CBSE (Central Board Secondary Education) increased the examination fees for classes 10 and 12 of the 2020 boards, with no profit no loss principle, from Rs. 750 to Rs 1500, for all categories of students, including SC/ST candidates for all schools throughout India...

Tips for exam preparation

Students often get nervous during their exams. The reason behind this nervousness is either a lack of confidence or a lack of preparedness. To overcome these fears students are advised to do their preparation in such a way that will retain their confidence. For this...

NCERT NTSE Admit Card 2020 released - know more

Introduction: NTSE 2020 National Talent search examination is conducted by NCERT to take out the students who excel in science. It is organized to measure and let the students with talent outshine in their coming future. This talent search exam is taken in 2 stages....

Studies Today