Short Question Answers : Composition and Structure of Atmosphere | Geography Class 11 - Humanities/Arts PDF Download

Q. 1. What is atmosphere ?
Ans. An envelope of gases around the earth.

Q. 2. Which are the two major gases constituting the atmosphere ?
Ans. Nitrogen and oxygen.

Q. 3. What is the percentage of nitrogen gas present in atmosphere ?
Ans. 78%.

Q. 4. What is the percentage of oxygen gas present in the atmosphere ?
Ans. 21%.

Q. 5. Why is atmosphere held to the earth ?
Ans. Due to force of gravity.

Q. 6. Name two gases found in the upper layers of atmosphere.
Ans. Argon, Helium.

Q. 7. Which rays are absorbed by ozone gas ?
Ans. Ultra-violet rays of the sun.

Q. 8. Which is the weather making layer of atmosphere ?
Ans. Troposphere.

Q. 9. What is the normal lapse rate of temperature ?
Ans. 1°C for 165 metres.

Q. 10. Which is the boundary between troposphere and stratosphere ?
Ans. Troposphere.

Q. 11. Which layer of atmosphere is called thermosphere ?
Ans. Stratosphere (Due to constant temperatures).

Q. 12. When has been a hole in ozone layer noticed  ?
Ans. In 1980, a hole in ozone layer on Antarctica.

Q. 13. What are the two harmful effects of ozone gas ?
Ans. Skin cancer and Blindness.

Q. 14. What is the use of Ionosphere ?
Ans. It reflects the radio waves back to the earth.

Q. l5. What are the two causes of depletion of ozone layer ?
Ans. Use of carbons (industrialisation) and Deforestation.

Q. 16. What is the function of dust particles in atmosphere ?
Ans. These cause fog, clouds and absorb insolation.

Q. 17. Name the town from where Indian daily weather maps are published.
Ans. Pune.

Q. 18. Name the science which studies the atmospheric conditions.
Ans. Meteorology.

Q. 19. Name the main elements of atmosphere.
Ans. (i) Gases (ii) Dust particles (iii) Water vapour.

Q. 20. Name the different layers of atmosphere.
Ans. (1) The troposphere—the lowest layer
(2) The stratosphere—layer next to troposphere
(3) Ozonesphere—zone of ozone gas
(4) Ionosphere—zone of ion gas
(5) Exosphere—the uppermost layer.

Q. 21. Define the climate of a place. How do you determine it ?
Ans. Climate is the average weather of a place over a long period of time. Climate is the composite picture of the daily weather. Climate is everlasting and does not change often. It is similar year after year. Studies of climate are based on the data relating to the last 30—40 years. It is the average of climatic conditions of an area over a long period.

Q. 22. Name the elements of weather.
Ans. The atmospheric conditions which make up the weather of place are known as elements of weather. These are :
(i) Temperature (ii) Pressure
(iii) Winds (iv) Sunshine
(v) Humidity (vi) Cloudiness
(vii) Rainfall (viii) Mist and fog.

Q. 23. Name the major controls of climate.
Ans. The factors which change the climate from place to place are known as the elements of climate.
(i) Latitude
(ii) Altitude
(iii) Distribution of land and water
(iv) Pressure
(v) Prevailing winds
(vi) Ocean currents
(vii) Mountain  barriers.

Q. 24. ‘Water vapour acts like a Blanket.’ Discuss.
Ans. Water vapour also decreases from the equator towards the poles. Water vapour absorbs parts of the insolation from the sun, and thus, reducing its amount reaching the earth’s surface. It also preserves the earth’s radiated heat. It thus, acts like a blanket allowing the earth neither to become too cold nor too hot. Conditions of stability and instability in the air are greatly influenced by the role of water vapour.

Q. 25. Explain the importance of ozone gas.
Ans. Ozonosphere extends between 10-50 km. above the surface of earth. It acts as a filter and absorbs the ultra violet rays radiating from the sun. These rays do not reach the earth. It shields the life on the earth from intense, harmful form of energy.
Q. 26. Explain the significance of atmosphere to man.
Ans. (i) Atmosphere makes the earth habitable.
(ii) It contains life-giving gases like oxygen and nitrogen for animal and plant life.
(iii) It is the storehouse of water vapour which leads to precipitation.
(iv) It protects us from millions of falling meteors.
(v) It absorbs ultra-violet rays.
(vi) It acts as an air conditioner by moderating the extremes of heat and cold.

Q. 27. (a) Write a note on ozone layer of the atmosphere. (b) Why is it depleting ? Where has been a hole in this layer found ? (c) What are its harmful effects ?
Ans. Ozone Layer. A thick layer of ozone gas exists  in upper atmosphere. This layer is useful as it absorbs ultra-violet rays of the sun. Due to excessive use of chemicals and carbons, (which react with Ozone layer), the ozone layer is being depleted. The atomic explosions also deplete the ozone layer. In 1980, a hole in the ozone layer was noticed over Antarctica.

Through this hole, ultra-violet rays will reach the earth. These rays are harmful as these cause skin cancer. It may cause blindness.

Q. 28. Name the main constituents of the pure dry air.
Ans. The atmosphere mainly consists of three elements : (i) Gases (ii) Water vapour (iii) Dust particles.
About 99% of the atmosphere consists of two gases.
(a) Nitrogen—78%
(b) Oxygen—21%
The remaining 1% is composed of a number of gases like hydrogen, argon, ozone, helium, carbon dioxide.

Q. 29. Define Atmosphere. (TBQ)
Ans. Atmosphere is a vast expanse of air which envelopes the earth all around. It represents the gaseous realm of the earth. It is held to the earth by the force of gravity. It is, thus, an integral part of the earth. It is a very vital part of human existence on the earth.

Q. 30. What is tropopause ?
Ans. Tropopause is the imaginary plane which separates the stratosphere from Troposphere. It is the boundary between the two layers of atmosphere.
It is known as ‘the ceiling of the troposphere’ as it is the upper layer of troposphere. Actually, it is a thin ‘transitional zone’ between the two layers.

Q. 31. Why is the troposphere considered to be the most significant layer of the atmosphere ?
Ans. Of all the l ayers of the atmosphere, troposphere is the most important in climatology due to the following reasons :
(i) This is the weather making layer of the atmosphere.
(ii) All the weather making processes are confined to this layer.
(iii) Great contrasts in climate and weather are observed in different areas due to changes of temperature in this layer.
(iv) The presence of most of the water vapour in this layer is responsible for condensation, clouds and precipitation.
(v) Dust particles give rise to fog, clouds, smog, etc. in this layer.
(vi) Convection currents are confined to this layer for the heating and cooling of the atmosphere.
(vii) The air is unstable in this zone and gives rise to atmospheric disturbances like storms, cyclones.