Table of Contents
Short Answer Type Questions:
Q1.What do you understand by atmosphere?
Answer
Atmosphere is a mixture of different gases and it envelopes the earth all round. It contains life-giving gases like oxygen for humans and animals and carbon dioxide for plants.
Q2.What are the elements of weather and climate?
Answer
The elements of weather and climate are temperature, pressure, winds, humidity, clouds and precipitation. These elements are subject to change and which influence human life on earth.
Q3.Describe the composition of atmosphere.
Answer
The atmosphere is composed of gases, water vapour and dust particles. Nitrogen constitutes 78.8%, oxygen constitutes 20.94% and argon constitutes 0.93%. Both gases together constitute 99% of the atmosphere. Other gases include are Carbon dioxide, Neon, Helium, Krypto, Xenon and Hydrogen.
Q4.Why is troposphere the most important of all the layers of the atmosphere?
Answer
Troposphere is the most important of all the layers of the atmosphere:→ All changes in climate and weather take place in this layer.→ This layer contains dust particles and water vapour→ All biological activities take place in this layer.
Q5.Describe the composition of the atmosphere.
Answer
The atmosphere is composed of gases, water vapour and dust particles. The given table specifies the constituent of atmosphere with their volume.
| Constituent | Formulae | % by Volume |
| Nitrogen | N2 | 78.08 |
| Oxygen | O2 | 20.95 |
| Argon | Ar | 0.93 |
| Carbon-dioxide | CO2 | 0.036 |
| Neon | Ne | 0.002 |
| Helium | He | 0.0005 |
| Krypton | Kr | 0.001 |
| Xenon | Xe | 0.0009 |
| Hydrogen | H2 | 0.0005 |
Nitrogen and Oxygen gases together constitute 99% of the atmosphere. Other gases include are Carbon dioxide, Neon, Helium, Krypto, Xenon and Hydrogen. The proportion of gases changes in the higher layers of the atmosphere in such a way that oxygen will be almost in negligible quantity at the height of 120 km. Similarly, carbon dioxide and water vapour are found only up to 90 km from the surface of the earth. Carbon dioxide absorbs a part of terrestrial radiation and reflects back some part of it towards the earth’s surface. It is largely responsible for the green house effect. Ozone is another important component of the atmosphere which absorbs the ultra-violet rays radiating from the sun and prevents them from reaching the surface of the earth.
Q6.Draw a suitable diagram for the structure of the atmosphere and label it and describe it.
Answer
The atmosphere consists of different layers with varying density and temperature. The column of atmosphere is divided into five different layers depending upon the temperature condition. They are: troposphere, stratosphere, mesosphere, thermosphere and exosphere.
• Troposphere: It is the lowermost layer of the atmosphere. Its average height is 13 km and extends roughly to a height of 8 km near the poles and about 18 km at the equator. This layer contains dust particles and water vapour. All changes in climate and weather take place in this layer. The temperature in this layer decreases at the rate of 1 C for every 165m of height. This is the most important layer for all biological activity.
→ Tropopause: The zone separating the tropsophere from stratosphere is known as the tropopause. The air temperature at the tropopause is about minus 80°C over the equator and about minus 45°C over the poles. The temperature here is nearly constant, and hence, it is called the tropopause.
• Stratosphere: It is found above the tropopause and extends up to a height of 50 km. It contains the ozone layer. This layer absorbs ultra-violet radiation and shields life on the earth from intense, harmful form of energy.
• Mesosphere: It lies above the stratosphere, which extends up to a height of 80 km. In this layer, once again, temperature starts decreasing with the increase in altitude and reaches up to minus 100 C at the height of 80 km. The upper limit of mesosphere is known as the mesopause.
• Thermososphere: It is the outermost layer of the atmosphere. It is located from 80 km with no definite upper limit. The air in this layer is very hot because heat coming from the sun strikes the thermosphere first.
→ Ionosphere: The lower layer of thermosphere is called ionosphere. It is located between 80 and 400 km above the mesopause. It contains electrically charged particles known as ions, and hence, it is known as ionosphere. Radio waves transmitted from the earth are reflected back to the earth by this layer. Temperature here starts increasing with height.
• Exosphere: The uppermost layer of the atmosphere above the thermosphere is known as the exosphere. This is the highest layer but very little is known about it. Whatever contents are there, these are extremely rarefied in this layer, and it gradually merges with the outer space.
Long Answer Type Questions :
Q1.Write about elements of weather and climate in detail.
Answer:
The main elements of atmosphere which are subject to change and which influence human life on earth are temperature, pressure, winds, humidity, clouds and precipitation. These elements act and react on each other. These elements determine the direction and speed of wind, amount of sunlight received, cloud formation and amount of rainfall. These in turn affect weather and climate. These factors behave differently in different places. All these elements are affected by a number of factors in turn. For example, temperature is affected by latitude and height; humidity is affected by distance from the sun and pressure is affected by height from sea level.
Q2.Write about the structure of atmosphere in detail.
Answer:
Structure of Atmosphere: The layers of atmosphere differ from one another with respect to density and temperature. On the basis of chemical composition the atmosphere is mainly divided into
- Homosphere
- Hetrosphere
1. Homosphere:
- It extends upto 90 km.
- It is uniform in chemical composition.
- It consists of three layers
- Troposphere
- Stratosphere
- Mesosphere
Troposphere:
- Lower most layer of atmosphere
- Average height is 13 km although it is roughly 8 km.
- The thickness of troposphere is greater at equation due to upward transportations of heat by conventional currents. This layer consists of dust particles and water vapours.
- The temperature decrease with height in this layer at a rate ldegree for every 165 m. this is known as Normal Lapse Rate.
- It is layer is important for all biological activities besides that all climatic and weather conditions takes place in this layer.
Tropopause:
- The upper limit of troposphere separating it from stratosphere is called tropopause. It is very unstable at a thin layer and very thin layers of 1.5 km thickness.
- The temperature of tropopause is -80degree centigrade censius at equator and -40 degree centigrade at poles.
- The jet planes at the other activities occur in this layer.
Stratosphere:
- It extends upto 50km.
- It is thicker at poles then at equator.
- The temperature is almost constant in its lower portion upto 20 km and their it gradually increases upto 50 km due to the presence of Ozone which absorbs UV rays.
- The temperature rises in the upper limits of the stratosphere as there are no clouds, no conventional currents, no dust particles and the air moves in the horizontal direction. The upper’ limit of stratosphere is called stratosphere which has concentration of Ozone gas.
Mesosphere:
- It extends from 50* to 90 km.
- Temperature decreases with height in this layer and false upto minus 100 degree centigrade at a height of 80-90 km. this is due to the clouds in high latitudes.
- The upper limit of Mesosphere is called as Mesopause.
2. Hetrosphere:
- It has heterogeneous chemical.
- It consist of two layers
- Ionosphere
- Exosphere
Ionosphere
- It extends from 80 to 400 km above the mesopause.
- It contains electrically charged particles known as ions.
Exosphere
- It is the uppermost layer of the atmosphere above the thermosphere.
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