chalk, etc. Air makes a very thick layer around the earth called atmosphere. It is extended from the earth’s surface to the space. Atmosphere also contains smoke, dust particles and water vapour in it. According to the height of the atmosphere and its nature, temperature and components are found different. On the basis of height, components and nature, atmosphere is divided into the following five layers.
i. Troposphere
ii. Stratosphere
iii. Mesosphere
iv. Thermosphere
v. Exosphere
Troposphere
It is the lowest and the thinnest layer of the atmosphere. It is extended up to the height of 16km from
the earth’s surface. The layer has the maximum pressure. It contains clouds. Changes in this layer cause the change in weather. This layer is highly influenced by our activities. Rain, hail, dew, and snow come form this layer. As the height in this layer increases, the temperature decreases. Major components of this layer are: N 2 , O 2 , CO 2 water-vapor, dust, etc.
Stratosphere
Stratosphere is found above the troposphere. It is extended between the height of 16 to 50 km from
the earth’s surface. It contains less oxygen and more ozone. The layer of ozone is called ozonosphere, which is a protective layer for us. It protects us from the harmful effects of ultraviolet rays coming from the sun. In this layer the temperature increases, with the increment of height. Jet planes fly in this layer. This layer is also influenced in some extent by our activities.
Mesosphere
Mesosphere is the third layer of the atmosphere. It is extended between 50-80 km height from the
earth’s surface. This layer has very less ozone in it. This layer has very strong wind in it. The wind blows eastward in winter and westward in summer. In this layer the temperature decreases when the height increases.
Thermosphere
Exosphere is the outermost layer of the atmosphere. It is extended beyond 72 km height from the
earth’s surface. This layer is extended 9600 km. It is the outer limit of the atmosphere. It is the uppermost layer; therefore here is so less gravity that some atoms of its components escape into the space. The major components of it are hydrogen and helium atoms.
Atmosphere Review
i. Temperature decreases as the height increases by 6.5 0 c per km.
ii. Upper most part of the troposphere is called tropopause.
iii. Troposphere is responsible to determine the weather and climate (e.g. Raining, cloud, storming, fogs etc.)
iv. Temperature increases as the height increases in stratosphere.
v. The upper layer of stratosphere is called stratopouse.
vi. The region where the ozone (O 3 ) lies in the stratopause is called ozone layer.
Ozone Layer
i. The ozone layer absorbs about 99% ultraviolet radiation coming from the sun.
ii. Ozonosphere is about 35 km thick.
iii. Ozone is formed the following ways by radiation
O 2 --- O+O
O 2 + O ---- O 3 (Ozone)
iv. The reduction of ozone layer due to chloro fluoro carbon, methyl chloro form carbon tetra chloride and methyl bromide is called depletion of ozone layer.
Effects of depletion of ozone layer.
i. It causes skin burning, lung and breast cancer, leukemia, blindness
ii. Growth of aquatic and amphibian plants are affected.
iii. Loss of productivity of living beings
iv. The depletion of O 3 layer may bring about significant changes in climate and cause green house
effect.
v. The depletion of ozone layers causes eye cancer in cattles.
Protection of ozone layer
i. By banning the production and use of CFC.
ii. By bringing awareness of ozone depletion in people.
iii. By recapturing CFC released from the air conditioners, refrigerators and other machinery using
them.
Green House Effect
i. The house made up of green glasses which can trap the solar radiation in it is called a green house.
ii. Off season fruits and vegetables can be grown with the help of green house.
iii. Carbon dioxide, nitrous oxide, methane; CFC, water vapour protect the solar radiation to wards
the earth. That means these gases help the earth to act as a green house. So these gases are called
green house gases and when amount of these gases increased the temperature of the earth is also
increased. This increment in temperature is called green house effect.
Effects of green house effect
i. It increases the temperature of the atmosphere
ii. On human, it helps spreading diseases like malaria.
iii. It helps breeding, growth and spreading of insects.
iv. Reduces crop yields by reducing the soil moisture.
v. The changes in climate pattern changes the crop pattern.
Ways of controlling green house effect
i. By increasing forestation.
ii. By reducing the use of fossil fuels.
iii. By banning deforestation.
iv. By banning the use of CFC.
v. By using unleaded petrol in vehicles.
vi. By using biogas for domastic purposes.
Industrial gases
i. The gas like SO 2 , CO 2 , CO, NO 2 dust and smoke are produced by industries are called industrial gases.
ii. The increment in the amount of industrial gas in the atmosphere pollute the air. Which is called air
pollution.
Effects of air pollution
i. Produce diseases of neck, breast and longs.
ii. Leukemia
iii. Acid rain
iv. Raise in temperature)
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