# Class 9 Social Science MCQ Chapter 7 Atmosphere Structure, Air Pressure and Wind System

Class 9 Social Science MCQ Chapter 7 Atmosphere Structure, Air Pressure and Wind System, Class 9 Social Science MCQ Question Answer, Class 9 Social Science Multiple Choice Question Answer to each chapter is provided in the list of SCERT Social Science Class 9 Objective Types Question Answer so that you can easily browse through different chapters and select needs one. Class 9 Social Science MCQ Chapter 7 Atmosphere Structure, Air Pressure and Wind System can be of great value to excel in the examination.

## SCERT Class 9 Social Science MCQ Chapter 7 Atmosphere Structure, Air Pressure and Wind System

SCERT Class 9 Social Science MCQ Chapter 7 Atmosphere Structure, Air Pressure and Wind System Notes covers all the exercise questions in SCERT Science Textbooks. The NCERT Class 9 Social Science MCQ Chapter 7 Atmosphere Structure, Air Pressure and Wind System provided here ensures a smooth and easy understanding of all the concepts. Understand the concepts behind every chapter and score well in the board exams.

Atmosphere Structure, Air Pressure and Wind System

Chapter – 7

GEOGRAPHY

### Multiple Choice Questions & Answers

1. Where is the Ozone layer located?

(a) Troposphere.

(b) Stratosphere.

(c) Mesosphere.

(d) Thermosphere.

Ans: (b) Stratosphere.

2. What is the amount of oxygen in the atmosphere in terms of volume?

(a) 20.94%

(b) 29.01%

(c) 32.47%

(d) 78.08%

Ans: (a) 20.94%.

3. The most important reasons for air movement is____

(a) Humidity difference.

(b) Pressure difference.

(c) Gravitational force.

(d) Centrifugal force.

Ans: (b) Pressure difference.

4. The instrument used for determination of wind velocity is____

(a) wind vane.

(b) Anemometer.

(c) Beanfort scale.

(d) Hydrometer.

Ans: (b) Anemometer.

5. The unit of wind velocity is____

(a) Knot.

(b) Millibar.

(c) Percentage.

(d) Degree.

Ans: (a) Knot.

6. Monsoon wind belongs to which of the following class?

(a) Local winds.

(b) Primary circulation.

(c) Secondary circulation.

(d) Permanent wind.

Ans: (c) Secondary circulation.

7. The name of the cyclone formed in the coastal region of the Pacific Ocean in the east is____

(a) Cyclone.

(b) Hurricane.

(c) Willy-willy.

(d) Typhoon.

Ans: (d) Typhoon.

8. Which gas readily absorbs heat?

(a) Oxygen.

(b) Carbon di oxide.

(c) Nitrogen.

(d) Methen.

Ans: (b) Carbon di oxide.

9. What is the other name of thermosphere?

(a) Lithosphere.

(b) hydrosphere.

(c) ionosphere.

(d) troposphere.

Ans: (c) ionosphere.

10. Where do the northern lights occur?

(a) troposphere.

(b) lithosphere.

(c) ionosphere.

(d) thermosphere.

Ans: (d) thermosphere.

11. In which layer is the temperature well above 300°C?

(a) exosphere.

(b) troposphere.

(c) thermosphere.

(d) mesosphere.

Ans: (a) exosphere.

12. Which has the lowest temperature in the atmosphere?

(a) ionosphere.

(b) mesosphere.

(c) stratosphere.

(d) lithosphere.

Ans: (b) mesosphere.

13. Which is not a fixed component of the atmosphere?

(a) dust.

(b) particles.

(c) water vapour.

(d) pebbles.

Ans: (d) pebbles.

14. Which protects the earth from meteors?

(a) thermosphere.

(b) stratosphere.

(c) troposphere.

(d) hydrosphere.

Ans: (a) thermosphere.

15. The thermosphere consists of electrically charged particles called____

(a) milibar.

(b) ions.

(c) feho.

(d) smoke.

Ans: (b) ions.

16. Wind movement is basically dependent on____

(a) temperature pressure.

(6) temperature difference.

(c) Pressure difference.

(d) Primary circulation.

Ans: (b) temperature difference.

17. What force acts negatively in determining wind velocity?

(a) gravitational.

(b) centrifugal.

(c) frictional.

(d) coriolis.

Ans: (c) frictional.

18. Where is the amount of coriolis highest?

(a) equator.

(b) sea.

(c) poles.

(d) hemisphere.

Ans: (c) poles.

19. What does isobar mean?

(a) equal value.

(b) equal pressure.

(c) equal weight.

(d) equal height.

Ans: (c) equal weight.

20. Atmospheric pressure becomes at the height of____

(a) wind level.

(b) sea level.

(c) base of atmosphere.

(d) bottom of sea.

Ans: (b) sea level.

#### Very Short Answer Type Questions:

1. Define atmosphere.

Ans: The gaseous envelope of air that surrounds the earth is known as atmosphere.

2. Which gas does readily combine with other elements?

Ans: Oxygen readily combines with other elements by the process of oxidation.

3. Which gas readily absorbs heat?

Ans: Carbon dioxide.

4. What does ozone gas do in the atmosphere?

Ans: Ozone gas absorbs the harmful ultraviolet rays of the sun and protects the living world from it.

5. What is the height of the troposphere in equatorial region?

Ans: 16 km.

6. What is the height of the troposphere in the polar region?

Ans: 10 km.

7. What does troposphere mean?

Ans: The word troposphere is derived from the Greek word ‘tropos’ which means turbulence or mixing.

8. What is the other name of thermosphere?

Ans: The thermosphere is also known as the ionosphere.

9. Where do the northern lights occur?

Ans: The northern lights occur in the thermosphere.

10. From what do the thermosphere protect the living world?

Ans: The thermosphere protects us from meteors and obsolete satellites.

11. What is atmospheric pressure?

Ans: Air has weight as it is made up of number of gases. It therefore, exerts a pressure called atmospheric pressure.

12. What is wind?

Ans: Wind is air in motion. It is a horizontal movement of air which is due to unequal heating of the air by the sun, giving rise to pressure belts.

13. What is the other name of equatorial pressure belt?

Ans: Equatorial low pressure belt is also known as belt of calm or Belt of doldrums.

14. Why is the study of air pressure significant?

Ans: The study of air pressure is of great importance because:

(i) weather forecasting is dependent on it.

(ii) Weather is influenced by it.

(iii) it creates wind.

15. What are the two types of air movement?

Ans: Horizontal and vertical.

16. What is the basic reason for the occurrence of pressure gradient?

Ans: The pressure gradient results from the pressure differences of the region.

17. What is centrifugal force?

Ans: Due to the earth’s rotation on its axis all outward force is generated from its centre. This is centrifugal force.

18. What is wind vane?

Ans: The instrument which helps in determining the correct direction of wind is known as wind vane.

19. What is cyclone?

Ans: The state of atmospheric circulation in which high velocity wind takes a cyclic path around a low pressure centre is called cyclone.

20. What is the other name of anticyclone?

Ans: As the atmospheric pressure become the highest at the centre of an anticyclone it is also known as high pressure centre.

21. What is ridge?

Ans: When the high pressure cell of an anticyclone becomes elongated instead, it is known as ridge.

22. Where are the anticyclones found?

Ans: The anticyclones are formed in the sub-tropical and high latitude regions of both the hemisphere of the earth.

23. What are the different types of anticyclone?

Ans: Anticyclones are of two types:

(i) Sub-tropical warm core anticyclone.

(ii) High latitude core cold anticyclone.

24. What are the various Fronts?

Ans: Fronts are classified into four categories.

They are:

(i) Cold front.

(ii) Warm front.

(iii) Stationary front.

(iv) Occluded front.

25. Name three different types of coastlines.

Ans: Three different types of coastlines are:

(i) Ria, Atlantic or Iran’s verse coast.

(ii) Dalamation, Longitudinat or Pacific Coast.

(iii) Fiord coastline.

26. What are the two types of glaciers?

Ans: (i) Continental glaciers.

(ii) Mountain glaciers.

27. What is the significance of delta?

Ans: The deltas have rich alluvial soils and abundant water supply from river channels. These features of delta is helpful in inland navigation. Delta also provides supply of water for irrigation and fertile soil for agriculture.

1. What are the methods of wind erosion?

Ans: Wind erosion may be of three types:

(i) Deflation: This involves lifting and flouring away loose materials, after exploration and weathing from the ground resulting in formation of large depression called deflation on hollow. Oases may be formed in this manner e.g. the Qattara Depression of the Share, 500 m. below the sea level.

(ii) Abrasion: the wind derives sand and dust particles against an exposed rock. This is sand blasting.

(iii) Attrition: When the sand blown particles roll against one another, or are is collision they become rounded and smaller in size.

2. Why the sub-tropical pressure belt is called the horse-latitude?

Ans: The sub tropical pressure belt is called the horse-latitude as the name is based on the experience of sailors crossing the Atlantic ocean from Europe to the West Indies.

In the olden days the ships used to take horses along with passengers and other cargo. When the boats reached the belt of sub-tropical high pressure they would not move due to the calm condition and the weight of the cargo. Captain of the ships resorted to throwing the horses into the sea in order to reduce the load and proceed on their voyage. Thus the name horse-latitude came into existence.

3. What are the effects of tropical cyclone?

Ans: Tropical cyclones are quite violent, destructive and harmful in nature. Such cyclonic storm remains active for long period of time covering a large area of the earth’s surface. Every year there is huge loss of lives and properties due to such tropical cyclones in south-eastern part of North America, eastern part of Japan, and East coastal region of india.

4. Define stationary front and occluded front.

Ans: The front which does not help shifting of air mass concerned and remain in static condition is called stationary front. When a new front is formed with mixed characteristics as a result of the mixing of cold and warm front with the changing properties it is called occluded front.

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