21 Apr 2022

Samacheer Kalvi 9th Geography Unit 3 Answers

Samacheer Kalvi 9th Social Science – Geography Unit 3 Book Back Answers:

Samacheer Kalvi 9th Standard New Social Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 9 New Syllabus 2021 to 2022 Book Back Question & Answer available for both English and Tamil Mediums. Class 9 Social Geography Book Unit 3 – Atmosphere Answers/Solutions are provided on this page. 9th Std Social Science History Book portion consists of 11 units, Geography Book portion consists of  8 units, Civics book portion consists of 6 units, and Economics book portion consists of 8 units, All Social Book Back One, and Two Mark Solutions are given below.

Check Unit wise and  Samacheer Kalvi 9th Social Science Book Back Solutions Answers PDF format for Free Download. English, Tamil, Maths, Science, and Social Science Book Back Question and Answer is available in PDF. Class 9th Standard Social Book Back Answers PDF. Check Social Science – History, Geography, Civics, Economics Answers below. See below for the 9th New Syllabus Book Back guide/Answers free PDF download:

Samacheer Kalvi 9th Social Science Book Back Solutions PDF:

9th Social Subject 1 Mark and 2 Mark Solutions PDF available below. Click the Download option to download the book back 1 Mark & 2 Mark questions and answers. Take the printout and use it for exam purposes. Samacheer Kalvi 9th Geography Unit 3 Answers are given below.

Geography Book Back Answers

Unit 3 – Atmosphere

I. Choose the Best Answer.

1. …………… is the most important gas for the survival of living
(a) Helium
(b) carbon-di-oxide
(c) oxygen
(d) methane
Answer: (c) oxygen

2. The lowest layer of the atmosphere is ……………
(a) Troposphere
(b) Stratosphere
(c) Exosphere
(d) Mesosphere
Answer: (a) Troposphere

3. …………. reflects radio waves.
(a) Exosphere
(b) Ionosphere
(c) Mesosphere
(d) Stratosphere
Answer: (c) Mesosphere

4. The average global surface temperature is …………….
(a) 12°c
(b) 13°c
(c) 14°c
(d) 15°c
Answer: (b) 13°c

5. The process of change of state of water from gaseous to liquid state is called ……………..
(a) Precipitation
(b) evaporation
(c) transpiration
(d) condensation
Answer: (d) condensation

6. The …………… is the chief energy source of the Earth.
(a) Sun
(b) Moon
(c) Stars
(d) clouds
Answer: (a) Sun

7. All types of clouds are found in the ……………….
(a) Troposphere
(b) Ionosphere
(c) Mesosphere.
(d) Exosphere
Answer: (a) Troposphere

8. …………….. clouds are called ‘Sheep clouds’.
(a) Alto-cumulus
(b) Alto-Stratus
(c) Nimbostratus
(d) Cirrocumulus
Answer: (a) Alto-cumulus

9. The Monsoons are ……………
(a) Prevailing winds
(b) Periodic winds
(c) local winds
(d) none of the above
Answer: (b) Periodic winds

10. Dew in the form of ice crystals is called ………….
(a) frost
(b) fog
(c) mist
(d) sleet
Answer: (d) sleet

11. ……………. is called the eye of the storm.
(a) Pressure
(b) wind
(c) cyclones
(d) snow
Answer: (c) cyclones

12. The vertical movement of air is called ……………
(a) Wind
(b) storm
(c) Air current
(d) drift
Answer: (c) Air current

II. Match the following:

1. Meteorology — wind speed
2. Climatology — direction of the wind
3. Anemometer — cirrus
4. Wind Vane — study of climate
5. Mare’s Tail — study of weather
6. Leeward side — Australia
7. Willy willy — rain shadow region

1. (e)
2. (d)
3. (a)
4. (b)
5. (c)
6. (g)
7. (f)

III. Answer the following briefly.

1. Define the atmosphere.
The blanket of air that surrounds the Earth is called the atmosphere.

2. Name the different atmospheric layers.
The different atmospheric layers are Troposphere* Stratosphere, Mesosphere, Thermosphere, and Exosphere.

3. Mention the factors that affect the climate.
The factors that affect the climate are

  • Distance from the equator
  • Altitude
  • Nearness to the sea
  • Nature of the prevailing winds
  • Mountain barrier
  • Cloud cover
  • Ocean currents
  • Natural vegetation

4. What is insulation?
The amount of heat received from the sun in the form of short waves is called insulation (or) incoming Solar Radiation.

5. What are isotherms?

  • Isotherms are imaginary lines drawn on maps, connecting points that have equal temperatures. .
  • Temperature varies from place to place, season to season and continent to continent.

6. Write a short note on ‘Lapse rate’.

  • Altitude refers to the height above sea level.
  • The temperature decreases at the rate of 1°C far every 165 mts of height. This is called “Normal Lapse rate”.

7. What are the processes responsible for heating the atmosphere?
The processes responsible for heating the atmosphere are Radiation, Conduction, Convection and Advection.

8. Mention the planetary wind system of the earth.
The winds which constantly blow in the same direction throughout the year are called the planetary winds. They are also called as permanent winds (or) the prevailing winds.

9. Write a short note on:
(a) Trade winds (b) Roaring Forties
(a) Trade winds:

  1. Trade winds blow from the subtropical high pressure belt to the Equatorial low pressure belt in both the hemispheres.
  2. They blow with great regularity, force and in a constant direction throughout the year. They are very helpful to the traders.

(b) Roaring forties:

  1. Westerlies are the permanent winds.
  2. They blow from South West to North East in the Northern hemisphere and North West to South East in the Southern hemisphere.
  3. The velocity of westerlies become so vigourous and fast to be called Roaring forties at 40°.

10. How are clouds formed?

  1. Large amount of water evaporates each day from the surface of the Sea.
  2. This is the principal source of atmospheric moisture.
  3. Cool moisture laden air, gets collected around particles like dust, salt content from the sea, smoke, etc, and forms clouds.
  4. Sometimes mixing warmer and cooler air also produces clouds.

11. What are the different types of rainfall?
Based on the mechanisms of raising the air, there are three types of rainfall.

  1. Convectional rainfall
  2. Frontal (or) cyclonic rainfall
  3. Orographic rainfall

12. What is Precipitation? What are the different forms of precipitation?

  1. Falling down of condensed water vapour in different forms is called Precipitation.
  2. The main forms of precipitation are Drizzle, rain, sleet, snow, hail, etc.

13. Write short notes on:
a. Drizzle b. rain c. sleet d. snow e. heat
a. Drizzle:

  1. Falling of numerous uniform minute droplets of water with diameter of less than 0.5 is called a drizzle mm from low clouds.
  2. Sometimes drizzles are combined with fog and hence reduce visibility.
  3. Rain:
  4. Rain is the most widespread and important form of precipitation in places having temperatures above the freezing point.
  5. It occurs only when there is abundant moisture in the air. The diameter of a rain drop is more than 5 mm.
  6. Sleet:
  7. Sleet refers to precipitation in the form of pellets made up of transparent and translucent ice.
  8. This precipitation is a mixture of snow and rain.
  9. Snow:
  10. Snow is formed when condensation occurs below freezing point.
  11. It is the precipitation of opaque and semi opaque ice crystals.
  12. When these ice crystals collide and stick together, it becomes snowflakes. ‘
  13. Heat:
  14. Is the energy which makes objects hot, while temperature measures the intensity of heat.

14. How are Cyclones classified?
Cyclones Can be classified into

  1. Tropical cyclones
  2. Temperate cyclones
  3. Extra-Tropical cyclones.

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