Atmosphere
M.P. Board Class 7th Social Science
Chapter 8
Atmosphere
Online Lecture
Textual Exercise
Choose the correct alternative from the following:
1. In which layer of the atmosphere does weather phenomenon take place?
(a) Troposphere
(b) Stratosphere
(Q) Mesosphere
(d) Outer space
Ans. (a) Troposphere
2. Which gas is found the most in atmosphere?
(a) Ozone
(b) Oxygen
(c) Carbon-di-oxide
(d) Nitrogen
Ans. (d) Nitrogen
Fill in the blanks:
- Ozone gas protects the earth from the harmful ……………….. rays.
- ……………. is a life going gas for humans.
- Temperature is found constant in …………….. layer of atmosphere.
- Electrically charged particles are found in ……………..
- The atmosphere extends to a height of ……………. km from sea level.
Ans.
- ultra violet
- Oxygen
- stratosphere
- thermosphere
- 1600
Short Answer Type Questions
1. What is atmosphere?
Ans. The cover of the air around the earth is called the atmosphere. It has many gases, dust particles and poisonous gas.
2. Name the gases found in atmosphere.
Ans. The different gases found in the atmosphere are:
Nitrogen, Oxygen, Carbon dioxide, Hydrogen, Ozone and Helium. Nitrogen is found in the largest quantity..
3. Which are the layers of atmosphere? Name them.
Ans. The layers of atmosphere:
- Troposphere
- Stratosphere
- Mesosphere
- Thermosphere
- Exosphere.
Long Answer Type Questions
1. Describe the structure of atmosphere.
Answer:
The changes in temperature at various attitudes divide the atmosphere into 5 layers.
- Troposphere
- Stratosphere
- Mesosphere
- Thermosphere
- Exosphere
1. Troposphere:
It extends to a height of 8 km at the poles and 18 km on equator. Dust particles and water vapor are found in this layer. All kinds of weather phenomenon like clouds, rainstorm etc. is observed in this layer. All types of life forms are found in this layer. This layer is also known as dynamic layer.
2. Stratosphere:
The second layer of the atmosphere is known as stratosphere. The temperature in this layer is constant till 20 kms. height and then slowly increases.
3. Mesosphere:
The height of this layer is 50 to 80 km from the sea level. The variation in temperature is less in this layer as water vapor, clouds and dust are found less and fast wind blows here.
4. Thermosphere:
The thermosphere starts from the height of 80 km from sea level. The density of air is very less in this layer. The temperature increases with height in this layer. Two layers of gases are found here. One is the ozone layer and the other is the ion layer.
The ozone layer is spread at a height of 32 to 80 km from the earth. The ion layer is found at a height of 80 to 400 km. from earth. The electrically charged particles stop the radio waves transmitted from the earth and return it back to the earth. In this way we can listen to various radio programmers.
5. Exosphere:
This is the outermost layer of die atmosphere the upper limit of this layer is uncertain. The density of air is the least here.
2. What is the importance of atmosphere?
Ans. The atmosphere is very important to us. It protects the life on earth by reflecting back the harmful ultra violet rays of the sun. It controls die extremes of temperature because of which moderate temperature is experienced in many parts of earth; It acts as the medium to send radioactive rays from one place to another on earth.
It is atmosphere, which makes possible earth movement of the airplanes. The seasonal changes on earth like balance of temperature, movement of wind, rain etc. is possible due to atmosphere. The atmosphere also contains life giving and life protecting gases. Thus, our atmosphere is of great importance.