Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere

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Tamilnadu Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere

Atmosphere Textual Exercise

I. Choose the Best Answer.

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

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

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

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

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere

Question 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

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

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

Question 8.
…………….. clouds are called ‘Sheep clouds’.
(a) Alto-cumulus
(b) Alto-Stratus
(c) Nimbo-stratus
(d) Cirro-cumulus
Answer:
(a) Alto-cumulus

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

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

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

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere

Question 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.

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere 1
Answer:
1. (e)
2. (d)
3. (a)
4. (b)
5. (c)
6. (g)
7. (f)

III. Answer the following questions briefly.

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

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

Question 3.
Mention the factors that affect the climate.
Answer:
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

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

Question 5.
What are isotherms?
Answer:

  • 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.

Question 6.
Write short note on ‘Lapse rate’.
Answer:

  • 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”.

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

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere

Question 8.
Mention the planetary wind system of the earth.
Answer:
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.

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

Question 10.
How are clouds formed?
Answer:

  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.

Question 11.
What are the different types of rainfall?
Answer:
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

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

  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.

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere

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

b. Rain:

  1. Rain is the most widespread and important form of precipitation in places having temperatures above the freezing point.
  2. It occurs only when there is abundant moisture in the air. The diameter of a rain drop is more than 5 mm.

c. Sleet:

  1. Sleet refers to precipitation in the form of pellets made up of transparent and translucent ice.
  2. This precipitation is a mixture of snow and rain.

d. Snow:

  1. Snow is formed when condensation occurs below freezing point.
  2. It is the precipitation of opaque and semi opaque ice crystals.
  3. When these ice crystals collide and stick together, it becomes snowflakes. ‘

e. Heat:

  1. Is the energy which makes objects hot, while temperature measures the intensity of heat.

Question 14.
How are Cyclones classified?
Answer:
Cyclones Can be classified into

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

IV. Distinguish between the following.

Question 1.
Weather and climate.
Answer:

S.No. Weather Climate
(i) Weather is the study of atmospheric conditions for short duration over small areas. It is the study of the average weather condition observed over a long period of time for a larger area.
(ii) The weather changes very often; hour to hour and day to day. Climate is more (or) less permanent and remains the same always.
(iii) Study of weather is called meteorology. Study of climate is called climatology.

Question 2.
Land breeze and sea breeze.
Answer:

S.No. Land Breeze Sea Breeze
(i) During the night the land cools more rapidly than the ocean. Cool air sinks and forms high pressure. During the day the land masses get heated more rapidly than the oceans.
(ii) The wind blows from land to sea during the night is called land breeze. Heated air ascends and this causes low pressure on the adjoining ocean, therefore the wind blows from ocean to land in the afternoon. This is called sea breeze.

Question 3.
Windward side and Leeward side.
Answer:

S.No. Windward side     Leeward side
(i) The windward side of a mountain which faces the prevailing wind. The Leeward side of the mountain is the side sheltered from the wind.
(ii) It receives heavy rainfall. It receives very less rainfall.

Question 4.
Tropical cyclone and Temperate cyclones
Answer:

S.No.

Tropical cyclones

Temperate cyclones

(i) Tropical cyclone develop in the Inter tropical convergent zone. They are formed due to the differential heating of land & Sea. Temperate cyclones are formed along a front, where hot and cold air masses meet.
(ii) They often cause heavy loss of life and properly on the coasts and become weak after reaching the land masses. Temperate cyclones do not become weak like the Tropical cyclones on reaching the land.
(iii) Tropical cyclones are known as ‘cyclones’ in Indian ocean. Temperate cyclones are called western disturbances in India.

V. Give reasons.

Question 1.
Cyclones cause huge loss of life and property.
Answer:

  • Because they are formed due to the diffetential heating of land and sea.
  • Due to heavy rain, strong wind & large storm.
  • The destruction depends mainly on its intensity, its size and its location,
  • After the cyclone the devastation continues.

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere

Question 2.
Cloudy days are warmer than cloudless days.
Answer:
On a cloudy day some energy from the sun gets into the atmosphere through the clouds but can’t get out again, when this happens the heat builds up during the day, so it gets warmer outside.

Question 3.
Fog is dangerous for traffic.
Answer:

  1. Fog is a cloud form at the surface of the earth made of tiny water droplets suspended in the air.
  2. Visibility is the greatest problem with fog.
  3. Fog creates dangerous driving conditions and so it is dangerous for traffic.

Question 4.
Convectional rainfall is also called 4 O’ clock rain.
Answer:

  1. The convectional rainfall occurs regularly in the equatorial region in the evenings.
  2. The ascending moist air cools, condenses and results in convectional rainfall. So it is called 4 O’ clock rainfall.

Question 5.
Polar Easterlies are cold and dry. Why it is so?
Answer:

  • Polar Easterlies blow form the high pressure areas of the Polar highs at the North and South Poles towards low pressure areas within westerlies at high altitudes.
  • When air moves near the poles, cold temperatures shrink the air. So Polar Easterlies are cold and dry.

VI. Paragraph Questions.

Question 1.
Write a paragraph about the structure of the atmosphere.
Answer:
The blanket of air that surrounds the Earth is called the atmosphere. The five atmospheric layers are Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.
Troposphere: The lowest layer of the atmosphere is the troposphere. The Greek word ‘tropos’ means ‘turn’ or change. The layer extends up to 8 kms at the poles and up to 18 kms at the Equator. The temperature decreases with increasing height. Almost all weather phenomenon take place in this layer. Hence it is called weather making layer. The upper limit of the troposphere is called as tropopause.

Stratosphere: Stratosphere lies above the troposphere. It extends to a height of about 50 km above earth surface. Since this layer is a concentration of ozone molecules, it is also referred as ozonosphere. The temperature increases with increase in height in this layer. Large jet planes normally fly here. The upper limit of the stratosphere is called as stratopause. Mesosphere: Mesosphere extends between 50km and 80km. The temperature increases with increasing height. Radio waves transmitted from earth are reflected back to earth from this layer. Most of the meteors nearing the earth, get burned here. The uppermost limit of the mesosphere is the mesopause.

Thermosphere: Thermosphere exists above the mesosphere. It extends to about 600 km. The composition of gases in the lower thermosphere is more or less uniform, hence it is called ‘‘Homosphere”. The upper portion of the thermosphere has uneven composition of gases and hence it is referred as “Heterosphere”. Here the temperature increases with increasing height. Ionosphere is a layer of the thermosphere that contains Ions and free electrons.

Exosphere: The uppermost layer of the atmosphere is called exosphere. This layer is extremely rarefied with gases and gradually merges with the outer space. This zone is characterized by aurora Australis and aurora borealis.

Question 2.
Explain the different types of permanent winds.
Answer:
Westerlies are the permanent Winds that blow from the tropical high pressure belt to the sub polar low pressure belt in both the hemispheres. They blow from South West to North East . in the northern hemisphere and North West to South East in the southern hemisphere. The velocity of westerlies become so vigorous and fast to be called Roaring Forties at 40°, Furious Fifties at 50° and Screaming Sixties at 60° latitudes.

Question 3.
How are clouds classified? Explain them.
Answer:
According to their height, clouds are classified into the following types
• High clouds (6 – 20 km Height)
• Middle clouds (2.5 km – 6 km Height)
• Low clouds (ground surface to 25 km height)
These major types of clouds are further divided into different types on the basis of shape and structure.

  1. High clouds
    • Cirrus: Detached clouds in the form of white delicate fibrous silky filaments formed at the high sky (8000 meters to 12000 meters) are called Cirrus clouds. These clouds are dry and do not give rainfall.
    • Cirro-cumulus: White patched, sheet or layer like clouds composed of ice crystals. Cirro-stratus: Smooth milky transparent whitish clouds composed of tiny ice crystals.
  2. Middle clouds
    • Alto-stratus: Thin sheets of grey or blue coloured clouds in uniform appearance, consisting of frozen water droplets.
    • Alto-cumulus: clouds fitted closely together in parallel bands, called as ‘Sheep clouds’ or wool pack clouds.
    • Nimbo stratus: These are clouds of dark colour very close to the ground surface associated with rain, snow or sleet.
  3. Low clouds
    • Strato-cumulus: Grey or whitish layer of non-fibrous low clouds found in rounded patches at an height of 2500 to 3000 metres, associated with fair or clear weather.
    • Stratus: Dense, low lying fog-like clouds associated with rain or snow.
    • Cumulus: Dome-shaped with a flat base often resembling a cauliflower, associated with fair weather.
    • Cumulo-nimbus: Fluffy thick towering thunderstorm cloud capable of producing heavy rain, snow, hailstorm or tornadoes.

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere

Question 4.
How are cyclones formed? How are they classified?
Answer:
The term cyclone is a Greek word meaning “coil of a snake”. Cyclones are centres of low pressure where, winds from the surrounding high pressure area converge towards the centre in a spiral form. Due to the rotation of the earth, the cyclonic winds in the northern hemisphere move in anti clock wise direction, where as they move in clockwise direction in the southern hemisphere.
Cyclones can be classified into

Tropical cyclones, Temperate cyclones and Extra tropical cyclones . Tropical cyclones: Tropical cyclones develop in the Inter tropical convergence zone [ITCZ], They are formed due to the differential heating of land and sea.
Tropical cyclones are known as ‘cyclones’ in Indian ocean, ‘typhoons’ in the western pacific ocean, ‘hurricanes’ in the Atlantic and eastern Pacific ocean, ‘baguios’ in Phillipines and ‘willy willy’ in Australia. Tropical cyclones often cause heavy .loss of life and property on the coasts and become weak after reaching the landmasses.

Temperate cyclones: Temperate cyclones are formed along a front where hot and cold air masses meet in mid-latitudes between 35° and 65°N and S. Temperate cyclones do not become weak like the tropical cyclones on reaching the land. Temperate cyclone commonly occurs over the North Atlantic Ocean, North West Europe, Mediterranean basin. Mediterranean basin’s temperate cyclones extend up to Russia and India in winter. In India it is as called western disturbances.

Extra tropical cyclones: Extra tropical cyclones occur in the latitudes between 30° and 60° in both the.hemispheres. They are also called as mid-latitude cyclones. They collect energy from temperature differences which are found in higher latitudes. Extra tropical cyclones produce mild showers to heavy gales, thunderstorms, blizzards, and tornadoes.

Question 5.
Explain the different forms of precipitation.
Answer:
Precipitation
Falling down of condensed water vapour in different forms is called Precipitation. When the dew point is reached in the cloud water droplets become saturated and start to fall. Hence, they fall on the earth as precipitation.
The climatic conditions/ factors influencing the forms of precipitation mainly are:
• Temperature.
• Altitude
• Cloud type
• Atmospheric conditions.
• Precipitation process.
The main forms of precipitation include drizzle, rain, sleet, snow, hail, etc.
Drizzle: Falling of numerous uniform minute droplets of water with diameter of less than 0. 5 is called a drizzle.mm from low clouds. Sometimes drizzles are combined with fog and hence reduce visibility.

Rain: Rain is the most widespread and important form of precipitation in places having temperature above the freezing point. It occurs only when there is abundant moisture in the air. The diameter of a rain drop is more than 5 mm.

Sleet: Sleet refers to a precipitation, in the form of pellets made up of transparent and translucent ice. This precipitation is a mixture of snow and rain.

Snow: Snow is formed when condensation occurs below freezing point. It is the precipitation of opaque and semi opaque ice crystals. When these ice crystals collide and stick together, it becomes snowflakes.

Hails: Hails are chunks of ice (greater than 2 cm in diameter) falling from the sky, during a rainstorm or thunderstorm.
Hailstones are a form of solid precipitation where small pieces of ice fall downwards. These . are destructive and dreaded forms of solid precipitation because they destroy agricultural crops and human lives.

VII. Activity:

  1. Preparing chart of clouds at various atmospheric levels. – Individual Activity.
  2. Collecting proverbs clouds and rain related proverbs. – Individual Activity.
  3. Poem on ‘clouds’ and ‘rain’. – Individual Activity.
  4. Report writing observe the clouds for a week. Write your report about the shape and colours of the clouds. – Group Activity.
  5. Working models (a) Rain Gauge (b) Wind vane – Group Activity.
    • The teacher takes initiative to complete the following activities.
    • The students get the assistance of the teacher to complete the given task.
  6. Preparing bar diagram:
    (a) Collect the data of temperature of Kanyakumari, Delhi, Allahabad, and Itanagar for a day.
    (b) Also collect the data of rainfall received by Jaisalmer (Rajasthan), Mawsynram (Meghalaya), Nagapattinam, Coimbatore for a day. – Group Activity.
  7. Become a budding Meteorologist:
    Record the local weather condition of your place for a week. – Group Activity.
    Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere 2

Answer:
You can do this activity in groups under the guidance of your teacher.

In-text HOTs Questions

Question 1.
Why is Troposphere called as weather making layer?
Answer:
The troposphere is the lowest layer of the atmosphere. It is also known as the weather-making zone because all physical processes of weather, like wind, clouds, storms, rainfall, mist, fog and hail, occur here.

Atmosphere Additional Questions

I. Choose the correct answer.

Question 1.
This is a permanent gas of the atmosphere.
(a) Nitrogen
(b) Argon
(c) Methane
(d) Helium
Answer:
(a) Nitrogen

Question 2.
This gas helps in protecting the earth from radiation.
(a) Hydrogen
(b) Nitrogen
(c) Ozone
(d) CO2
Answer:
(c) Ozone

Question 3.
The upper most layer of the atmosphere is …………….
(a) Statrosphere
(b) Mesosphere
(c) Exosphere
(d) Thermosphere
Answer:
(c) Exosphere

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere

Question 4.
This precipitation is a mixture of snow and rain.
(a) Sleet
(b) Snow
(c) Hail
(d) Hailstones
Answer:
(a) Sleet

Question 5.
Humidity of the atmosphere is measured by the wet and dry bulb thermometer called ………….
(a) Anemometer
(b) Thermometer
(c) Hygrometer
(d) Barometer
Answer:
(c) Hygrometer

Question 6.
This is one of the most feared weather phenomenon.
(a) Snow
(b) Hailstones
(c) Sleet
(d) Hails
Answer:
(b) Hailstones

Question 7.
Tropical cyclones in India is known as ……………
(a) baguios
(b) willy willy
(c) hurricanes
(d) Cyclones
Answer:
(d) Cyclones

Question 8.
The wind blowing from the east is ……………
(a) Planetary winds
(b) Easterly winds
(c) Variable winds
(d) Local winds
Answer:
(b) Easterly winds

Question 9.
This is the wettest place of India.
(a) Mawsynram
(b) Western Ghats
(c) Shillong
(d) Pune
Answer:
(a) Mawsynram

Question 10.
This is the earth’s magnetic belt ………………
(a) Thermosphere
(b) Stratosphere
(c) Mesosphere
(d) Magnetosphere
Answer:
(d) Magnetosphere

II. Match the following.
(a)
Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere 3
Answer:
(a)
1. (e)
2. (a)
3. (b)
4. (d)
5. (c)

(b)
Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere 4
Answer:
(b)
1. (d)
2. (c)
3. (a)
4. (e)
5. (b)

III. Answer the following questions briefly.

Question 1.
Who discovered Nitrogen in Atmosphere? When?
Answer:
In 1772 CE Daniel Rutherford discovered Nitrogen in atmosphere.

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere

Question 2.
What are Auroras?
Answer:
Auroras are cosmic glowing lights produced by a stream of electrons discharged from the Sun’s surface due to magnetic storms that are seen as unique multicolored fire works hanging in the polar sky during mid night.

Question 3.
What are mountain barriers?
Answer:

  • The location of the mountains influence the climate of a place.
  • The mountain chains act as natural barrier for the wind.
  • Sometimes they prevent the entry of cold winds into the country (or) the’escape of monsoon winds, thus having a great influence over the climate.

Question 4.
What happens to atmospheric pressure with altitude?
Answer:

  • Air pressure decreases with altitude.
  • The air molecules became scattered and more widely spaced at higher altitudes.
  • The air pressure develops by 34 millibars per 300 metres increase in height.

Question 5.
What do you call the winds of a particular area?
Answer:

  • The winds that are blown in a particular locality for a short period of time are called the local winds.
  • The effects of these local winds are experienced only in that particular area.

Question 6.
Define the terms (a) Absolute humidity (b) Relative humidity.
Answer:
Absolute humidity: The amount of water vapour in the atmosphere is called Absolute Humidity.
Relative Humidity: The ratio between the amount of water vapour in the atmosphere and the amount of water vapour it can hold is Relative humidity.

IV. Distinguish between the following.

Question 1.
Conduction and Convection.
Answer:

Conduction Convection
Conduction is the transfer of heat from hot body to a cold body through contact. Convection is transfer of heat by movement or circulation of air in a mass.

Question 2.
Isobar and Isotherm.
Answer:

Isobar Isotherm
An Isobar is an imaginary line drawn through places having equal atmospheric pressure reduced to sea level. An imaginary line on a map connecting points having the same temperature

V. Give reasons.

Question 1.
Thermosphere is also referred as “Heterosphere”.
Answer:
The upper portion of the Thermosphere has uneven composition of gases and hence it is referred as “Heterosphere”.

Question 2.
The wind blows from ocean to land in the afternoon. Why?
Answer:

  1. During the day the land masses get heated more rapidly than the oceans.
  2. Heated air ascends and causes low pressure on the adjoining ocean.
  3. Therefore the wind blows from ocean to land in the afternoon.

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere

Question 3.
The sub-tropical high pressure are called “horse latitudes”. Why?
Answer:

  1. With little Water and food left for humans, sailors used to throw the horses into the sea in order to make the vessels lighter.
  2. Henceforth these belts (or) latitudes are called as “horse latitudes”.

Question 4.
“Water droplets fall on the earth as precipitation”. Why?
Answer:

  1. When the dew point is reached in the cloud, water droplets become saturated and start to fall.
  2. Hence they fall on the earth as precipitation.

VI. Paragraph questions.

Question 1.
Describe the “composition of the atniosphere”.
Answer:
(i) Atmosphere is a mixture of gases, water vapour and dust particles in different proportions.

(ii) Nitrogen (78%) and Oxygen (21%) are permanent gases of the atmosphere. They constitute 99% of the total composition and their percentages always remain the same without any change.

(iii) The remaining one percentage is occupied by Argon (0.93%), Carbon-di-oxide, (0.03%), Neon (0.0018%), Helium (0.0005%), Ozone (0.00006%) and Hydrogen (0.00005%). Krypton, Xenon and Methane are also present in trace. Water vapour (0 – 0.4%) is also found in the atmosphere, which plays an important role in predicting weather phenomenon.

(iv) The other solid particles present in the atmosphere includes dust particles, salt particles, pollen grains, smoke, soot, volcanic ashes etc.,
(v) Oxygen is most important for living organisms.
(vi) CO2 absorbs heat and keeps the atmosphere warm by insulation and radiation.
(vii) Nitrogen acts as a diluent and is chemically inactive.
(viii) Ozone helps in protecting the earth from radiation.
(ix) The solid particles in the atmosphere acts as nuclei on which water vapour condense to form precipitation.

Question 2.
How is the Orographic rainfall caused?
Answer:
Orographic rainfall, also called relief rainfall, is caused when air is forced to rise against a high mountain. The mountain barriers lying across the direction of air flow, force the moisture laden air rise along the mountain slope. This results in the cooling of the air, which leads to the formation of clouds and rain. This rainfall is called Orographic rainfall. The side of the ‘ mountain facing the wind is called the windward side and receives heavy rainfall. It is called the rainfed region. The other side of the mountain that does not face the wind is called the leeward side and receives less rainfall becomes rain shadow region.

VII. HOTs (Higher Order Thinking skills) Questions

Question 1.
Why is Troposphere called as weather making layer?
Answer:
‘Tropos’ means ‘turn’ (or) change. Almost all weather phenomenon takes place in this layer. Hence Troposphere is called as weather making layer.

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 3 Atmosphere

Question 2.
Cuddalore and Nagapattinam are always affected by cyclones. Why?
Answer:

  1. Coastal zone is exposed to natural forces including cyclones and Tsunamis.
  2. Cuddalore and Nagapattinam are situated on the Sea-Shore.
  3. Cuddalore and Nagapattinam are vulnerable to storms.
  4. During Summer Bay of Bengal subject to intense heat cause to raise the humid and unstable air masses that produce cyclone.

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