RBSE Class 11 Geography Notes Chapter 11 Atmosphere: Composition and Structure

Go through these RBSE Class 11 Geography Notes Chapter 11 Atmosphere: Composition and Structure contain important concepts so that students can score better marks in the exam.

Rajasthan Board RBSE Class 11 Geography Notes Chapter 11 Atmosphere: Composition and Structure

→ The thick envelope of air which surrounds the earth is called the Atmosphere.

→ The atmosphere is an integral part of the earth due to its gravitational force.

→ We can only feel the air, it has no colour, taste or odour.

→ Air is the basis of the life of all the creatures in the world without which no one can survive.

Importance of Atmosphere

  • There are many useful gases in the atmosphere (oxygen, nitrogen, carbon dioxide, hydrogen, argon).
  • We are protected from the harmful effects of ultraviolet rays due to the atmosphere.
  • Human life is influenced by the temperature and humidity present in the atmosphere.
  • The diverse natural vegetation, wildlife and human life are the gifts of the atmosphere.

RBSE Class 11 Geography Notes Chapter 11 Atmosphere: Composition and Structure

Composition of Atmosphere

  • Air is the sum total of gases, water vapour and dust particles. There are 9 types of gases in it.
  • Nitrogen (78.8%) and Oxygen (20.95%) gases are present in maximum quantity in the atmosphere.
  • Other gases in the atmosphere include Argon (0.93%), Carbon Dioxide (0.03%), Neon (0.0018%), Helium (0.0005%), Ozone (0.00006%), Hydrogen (0.00005%) and kryton.
  • Nitrogen is a gas that has no colour, smell, or taste.
  • Due to the Nitrogen gas, the influence of wind pressure, wind power and reflection of light is there.
  • It protects the things from burning and rapidly builds protein in trees and plants.
  • Oxygen is a life-sustaining gas. This gas is necessary for building many types of compounds as well as for burning of the objects.
  • Carbon dioxide is a heavy gas. This is produced by burning of objects.
  • Trees and plants use this gas in the process of photosynthesis.
  • At present, the volume of this gas is increasing in the atmosphere due to which global warming is on a rise and climatic changes have become visible.
  • Ozone is formed from three atoms of oxygen. This gas has a special significance in protection of earth.
  • Harmful ultraviolet rays coming from the sun are absorbed by ozone gas.

Water Vapour

  • Most of the water vapour is found in the lower layer of the atmosphere.
  • 90 per cent of the entire water vapour in the atmosphere is present up to an altitude of 8 km.
  • Water vapour is like a blanket for the Earth, which prevents the earth from being overheated or over-cooled.

Dust Particles

  • Due to the movement of air in the atmosphere, the presence of dust particle is a natural process.
  • Mud often contain minute particles of soil, dust, sea salt, volcanic ash and meteorites.
  • Due to the dust particles, the colour of the sky appears to be blue, and at the time of sunrise and sunset, the colour of the sky appears red.

Structure of the Atmosphere

  • In the Atmosphere, there are mainly five layers the Troposphere, the Stratosphere, the Mesosphere, the Ionosphere and the Exosphere or the Magnetosphere.
  • Troposphere is the lowest layer of the atmosphere, while Exosphere is the topmost layer.

RBSE Class 11 Geography Notes Chapter 11 Atmosphere: Composition and Structure

Troposphere

  • It is the lowest layer of the atmosphere, in which 75 per cent of the atmosphere is centered.
  • Its height is 8 – 10 km. on the Poles and 18 km. at the Equator.
  • All the climatic seasonal phenomena occur in this layer.
  • With the increase in altitude, the temperature decreases by 6.4°C at every 1000 meters, which is called Normal Lapse Rate.
  • Its upper layer is called the Tropopause, which is 1.5 km. thick.

Stratosphere

  • The height of this layer is considered to be 50 km. from the ground, it is thick on the Poles and thin on the Equator.
  • Due to the temperature being consistent in this layer it is called the stratosphere.
  • The Ozonosphere is considered to be part of this layer which is mainly spread between 15 to 35 km.
  • Ultraviolet rays coming from the sun are absorbed by the ozone layer.

Mesosphere

  • This layer extends above the stratosphere and up to a height of 80 km.
  • In this layer the temperature decreases. The temperature at its upper boundary goes down to -80°.
  • In this layer, air pressure is extremely low. The upper boundary of this layer is called the Mesopause.

Ionosphere

  • This layer is spread over 80-400 km. above the upper boundary of the Mesosphere.
  • The particles of gas found in this layer are electrically charged. These electrically-charged particles are called ions.
  • Aurora is also visible in this part. This layer is also called thermosphere.

Exosphere and Magnetosphere

  • It is the topmost layer of the atmosphere. In this layer, the air becomes very rare.
  • There is no upper boundary of this layer. Still, some scholars have estimated its boundary to be 1000 km.

Elements of Season and Climate

  • The weather is called the sum total of atmospheric conditions on a particular time at a particular location.
  • Temperature, air pressure, rainfall, wind and humidity are called the elements of the weather.
  • The uneven distribution of latitude, water and land, sea currents, air pressure, height from sea level, mountain obstruction, surface nature and air turbulence are considered to be the controlling factors of the weather.

RBSE Class 11 Geography Notes Chapter 11 Atmosphere: Composition and Structure

Atmosphere: Composition and Structure Notes Important Terms

→ Atmosphere: The thick layer of air circulating around the earth or the covering in which the mixture of different gases is found is called the atmosphere. Many gases are found in the composition of the atmosphere, in which nitrogen, oxygen, argon, and carbon dioxide are found in large proportions and hydrogen, neon, helium ozone, etc. are found in very small proportions.

→ Gravitation: Force of attraction found between two objects or substances. According to Newton’s law of gravity, two objects of matter are attracted to each other by gravitational force, which is directly proportional to the product of their mass and inversely proportional to the square of distance between them.

→ Hydrosphere: It constitutes all the water content on the surface of the Earth which is separate from the lithosphere and the atmosphere. Under this, the aquatic part comprised mainly in the form of seas, lakes, rivers, ice sheets, etc. is included.

→ Solar Radiation: The radiated energy from the surface of the sun, which travels at a speed of 1,86,000 miles per second, reaching the earth’s surface.

→ Insolation: Radiation energy from the Sun to the Earth or to other planets. According to the distribution of insolation, the world is divided into three main parts. Tropical zone, Temperate zone and Polar zone

→ Condensation: The process by which a substance is converted from vapour to liquid state. For example, the condensation of the water vapour in the atmosphere forms a cloud and the water vapour turns into water-its liquid form.

→ Meteorite Shower: Meteorites are part of the solar family. At the time of the origin of the planets, they were separated into space in the form of meteors. Sometimes, these meteors fall on the ground, this process is called Meteorite Shower.

→ Arid Zone or Arid Land: The region where the amount of rain is so low that it is inadequate for the development of vegetation. Generally, such area is considered Arid Zone.

→ Troposphere: The lowest layer of the atmosphere above the Earth, which extends from the surface to an average of 13 km. Its height is greatest on the Equator, which decreases gradually towards the Poles.

→ Stratosphere: The intermediate layer of the atmosphere which extends up to 50 km. above the troposphere. Its position is between the tropopause and the stratopause.

→ Mesosphere: The layer of atmosphere, ranging from 50 km. to 80 km. in which the temperature decreases along with increase in height. Below it, there is the stratopause and above it, there is the upper mesopause.

→ Ionosphere: An atmospheric belt which extends from approximately 50 km. to 500 km. above the height of the ground. Electrical and magnetic phenomena occur in this sphere and from here the radio waves are reflected.

→ Exosphere: The upper-most part of the atmosphere about which significant knowledge has not yet been gained. It is located at a height of approximately 640 km (400 miles) from the surface.

→ Normal Lapse Rate: The average rate of change in the temperature of the air with increase in altitude above the sea level, is the normal lapse rate. The temperature decreases to 0.6°C per 100 meter increase in height above the sea level. This is called Normal Lapse Rate or Environmental Lapse Rate.

→ Tropopause: The division border between the troposphere and the stratosphere in the atmosphere that separates the two layers. It is found in the form of a thin layer. Its thickness is about 1.5 km.

→ Ozonosphere: Atmospheric belt present at the lower part of the stratosphere, situated between the height of about 20 and 50 km, in which, concentration of ozone gas is primarily found.

→ Mesopause: At a height of about 80 km. from the surface, this is a thin layer located above the Mesosphere, in which the minimum temperature of the atmosphere is found. This layer of the minimum temperature in the atmosphere is called the Mesopause.

→ Thermosphere: The upper layer of the Earth’s atmosphere, which extends from the middle boundary to the upper boundary of the atmosphere. The temperature increases along with the increase in altitude in the Thermosphere.

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