Atmosphere- Science Notes

# Atmosphere

The earth is surrounded by air. Air is also found in soil, water and porous things like sponges, bricks, 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.

1. Troposphere

2. Stratosphere

3. Mesosphere

4. Thermosphere

5. Exosphere

1. 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: N₂, O₂, CO₂ water-vapour, dust, etc.

2. Stratosphere

Stratosphere is found above the troposphere. It is extended between the height of 16 to 50km 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.

3. Mesosphere

Mesosphere is the third layer of the atmosphere. It is extended between 50-80km 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.

4. 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 9600km. 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.

5. Exosphere

An exosphere is the uppermost layer of an atmosphere where the density is extremely low. An upward traveling molecule moving through the exosphere fast enough to attain escape velocity can escape to space with a low chance of collisions; if it is moving below escape velocity it will be prevented from escaping from the celestial body by gravity. In either case, such a molecule is unlikely to collide with another molecule due to the exosphere's low density.

# Atmosphere Review

a.    Temperature decreases as the height increases by 6.5⁰c per km.

b.    Upper most part of the troposphere is called tropopause.

c.     Troposphere is responsible to determine the weather and climate (e.g. Raining, cloud, storming, fogs etc.)

d.    Temperature increases as the height increases in stratosphere.

e.     The upper layer of stratosphere is called stratopouse.

f.      The region where the ozone (O₃) lies in the stratopause is called ozone layer.

# Ozone Layer

a. The ozone layer absorbs about 99% ultraviolet radiation coming from the sun.

b. Ozonosphere is about 35 km thick.

c. Ozone is formed the following ways by radiation

                                      O₂  ®      O+O

                                      O₂ + O ® O₃ (Ozone)

d. 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.

a.  It causes skin burning, lung and breast cancer, leukemia, blindness

b. Growth of aquatic and amphibian plants affected

c. Loss of productivity of living beings

d. The depletion of O₃ layer may bring about significant changes in climate and cause green house     effect.

e. The depletion of ozone layers causes eye cancer in cattles.

# Protection of ozone layer

a.    By banning the production and use of CFC.

b.    By bringing awareness of ozone depletion in people.

c.     By recapturing CFC released from the air conditioners, refrigerators and other machineries using them.

# Green House Effect

a.The house made up of green glasses which can trap the solar radiation in it is called a green house.

b.Off season fruits and vegetables can be grown with the help of green house.

c.   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

a.It increases the temperature of the atmosphere.

b.    On human, it helps spreading diseases like malaria.

c.     It helps breeding, growth and spreading of insects.

d.    Reduces crop yields by reducing the soil moisture.

e.     The change in climate pattern changes the crop pattern.

# Ways of controlling green house effect

a.    By increasing forestation

b.    By reducing the use of fossil fuels.

c.     By banning deforestation

d.    By banning the use of CFC

e.     By using unleaded petrol in vehicles

f.By using biogas for domestic purposes

# Industrial gases

a.    The gases like SO₂, CO₂, CO, NO₂ dust and smoke are produced by industries are called industrial gases.

b.    The increment in the amount of industrial gas in the atmosphere pollute the air is called air pollution.

# Effects of air pollution

a.    Produce diseases of neck, breast and longs.

b.    Leukemia

c.     Acid rain

d.    Raise in temperature)

# Exercise for Practice

   Answer the following questions.

1.   What is atmosphere? List the composition of different gases in the atmosphere?

2.   List the layers of the atmosphere.

3.   List the thickness of different layers of atmosphere.

4.   What is tropopause? Write the rate of decrease of temperature of troposphere with its height.

5.   Why is the troposphere denser?

6.   Which layer of atmosphere is called stratosphere? List its thickness.

7.   What characters does the stratosphere show?

8.   Which layer of atmosphere is responsible to absorb ultra violet rays? Name the matter that absorbs ultraviolet rays and remains in the atmosphere.

9.   Why lower layer of troposphere is is hotter?

10.  Write the event that happens in the troposphere.

11.  Write every short note about the distribution of temperature in the stratosphere.

12.  Write short note about wind below in the mesosphere.

13.  Why thermosphere is called ionosphere too?

14.  In which layer of atmosphere following events happen?

a.  Lightning and thundering

b.  Meteors produce streaks produce streaks of light.

c.  Radio waves are reflected to the earth

d.  Clouds are formed and showers rain

15.  Define

a.  Stratopause

b.  Ozonosphere

c.  Mesopause

d.  Mesosphere

16.  Why is temperature of upper layer of stratosphere more?

17.  What is ozone? Where is layer of ozone situated?

18.  What is meant by ozone layer? How is it formed?

19.  Which rays is absorbed by ozone layer? What are advantages to us from this act of the ozone layer?

20.  Write importance of ozone layer.

21.  What are measure matters which cause depletion of ozone layer?

22.  How should we take care of ozone layer?

23.  Ozone layer is security shield for living things in the earth. How?

24.  What is meant by ozone hole? What does it inform to living things of the earth; sign of goodness or danger to us? How?

25.  What is CFC and uses of it?

26.  Why is CFC banned?

27.  What are the effects of depletion of ozone layer?

28.  Define green house effect?

29.  What is meant by natural green house and artificial green house?

30.  Write the importance of natural green house?

31.  Write the uses of artificial green house.

32.  How is green house effect produced?

33.  What are measure matters which cause increase of green house effect?

34.  List the effects of increasing green house effect.

35.  List human activities which increase green house effect.

36.  Increasing green house effect is more dangerous to our country, Nepal, How?

37.  What should be our role to decrease the green house effect?

38.  Sketch a figure to show  natural green house

39.  Sketch artificial green house including its functioning.

40.  What is industrial gas?

41.  What are toxic industrial gases?

42.  What is meant by industrial pollution?

43.  What is meant by industrial smog?

44.  What is meant by acid rain? How is acid rain formed?

45.  Which industrial gases cause diseases of throat and thorax in human?

46.  Which industrial gases cause increase of global temperature?

47.  Which industrial gases cause acid rain?

48.  What is industrial pollution?

49.  List the effects of industrial pollution.