Longman Panorma Geography Solutions Solutions for Class 7 Social science Chapter 1 Our Environment are provided here with simple step-by-step explanations. These solutions for Our Environment are extremely popular among Class 7 students for Social science Our Environment Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Longman Panorma Geography Solutions Book of Class 7 Social science Chapter 1 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Longman Panorma Geography Solutions Solutions. All Longman Panorma Geography Solutions Solutions for class Class 7 Social science are prepared by experts and are 100% accurate.

Page No 28:

Question A.1:

Name the five layers of the atmosphere?

Answer:

The atmosphere of the Earth is divided into five layers based on their properties like composition, temperature and so on. Their names are as follows:

  1. Troposphere
  2. Stratosphere
  3. Mesosphere
  4. Thermosphere
  5. Exosphere
​​

 
 

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Question A.2:

How is the troposphere important for us?

Answer:

Troposphere is the densest layer of atmosphere that is composed of water vapour, dust particles and many other impurities. Due to this thickness, troposphere absorbs most of the heat radiated by the Earth's surface, thereby, maintaining the temperature of the surface. Also, this layer is characterised with several weather phenomena like cloud formations and thunderstorms.

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Question A.3:

What do you mean by the normal lapse rate of temperature?

Answer:

In troposphere, with increase in height, the density of air decreases and the temperature also starts falling. For every 165 metres, there occurs a ofall in temperature and this is known as the normal lapse rate of temperature.

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Question A.4:

What is the significance of the ozone layer?

Answer:

The ozone layer present in stratosphere is of great significance to human survival on the Earth. Ozone layer prevents the harmful ultraviolet radiation of the Sun from reaching the Earth's surface. If these rays would come to us directly, then they will cause problems like temperature rise and cancer.

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Question A.5:

Which layer of the atmosphere makes radio communication possible?

Answer:

The thermosphere layer of the atmosphere makes the radio communication possible on Earth. This layer is composed of several ions that reflect the radio waves back to Earth, making it possible to have wireless communication.

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Question B.1:

Troposphere and stratosphere

Answer:

Troposphere Stratosphere
It is the lowest layer of the Earth's atmosphere. It is the second layer from the surface of the Earth.
It extends up to a height of 8 km at the poles and 18 km at the Equator. This layer extends up to a height of 50 km from the Earth's surface.
Temperature decreases with increasing height. At the lower surface, temperature is constant and with increase in height, temperature also increases.
Weather phenomena are witnessed hence, the air is turbulent due to thunderstorms and clouds. There is absence of dust particles and clouds; therefore, the air is calm, thereby, providing smooth passage to aeroplanes.

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Question B.2:

Mesosphere and thermosphere

Answer:

Mesosphere Thermosphere
This layer extends to a height of 80 km from the the Earth's surface. This layer extends to a height of 450 km from the Earth's surface.
Temperature decreases with increase in height. Temperature increases with increase in height.
The layer separating mesosphere and stratosphere is called stratopause. The layer separating thermosphere and mesosphere is called mesopause.
Mesosphere lies above stratosphere. Thermosphere lies above mesosphere.

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Question B.3:

Tropopause and stratopause

Answer:

Tropopause: It is a thin layer that acts as a boundary between troposphere and stratosphere.

Stratopause: It is a thin layer separating stratosphere and mesosphere.

Page No 28:

Question C.1:

About 99% of the total mass of the atmosphere lies within a height of 32 km from the earth's surface.

Answer:

With the increase in height, a reduction in density of air is witnessed. All the layers of atmosphere rest on one another and the upper layer constantly exerts pressure upon the lower layer. This increases the compactness of air near the Earth's surface. This is the reason that almost 99% of the total atmospheric mass lies within the height of 32 km from the Earth's surface.

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Question C.2:

Air temperature decreases with increasing height in the troposphere.

Answer:

In troposphere, with increasing height, the density of air decreases and the temperature starts falling. This decrease in temperature is because of the phenomenon called normal lapse rate of temperature, that is, for every 165 metres, there occurs a fall in temperature of 1 oC.

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Question C.3:

The thermosphere is also called ionosphere.

Answer:

The layer present right above the mesosphere extending to a height of 450 km is the thermosphere. This layer is composed of electrically charged ions that are responsible for reflecting the radio waves back to the Earth's surface. Due to the presence of these ions, thermosphere is also known as ionosphere. 

Page No 28:

Question D.1:

With the help of a diagram describe the composition of atmosphere.

Answer:

Atmosphere of the Earth is composed of a large number of gases.It also includes dust particles, water vapour, pollen grains and other impurities like smoke and chemicals. They vary in their composition.

Nitrogen, which comprises 78% of the Earth's atmosphere, is a very essential element for maintaining the fertility of the soil along with the growth of plants and animals.

Oxygen, which is a life-giving gas, comprises 21% of the Earth's atmosphere. 

Carbon dioxide is needed by plants to make their own food. It also helps in maintaining the temperature of the Earth surface by absorbing the heat radiated from the Earth surface. Its composition is merely 0.03%, which is increasing day-by-day.

Other gases like argon, helium and neon and water vapour and dust particles covers the remaining 1% of the atmospheric composition.

The composition of atmosphere can be better understood with the help of the following diagram:
 

Page No 28:

Question D.2:

Draw a labelled diagram of the structure of the atmosphere and write about the characteristics of its different layers.

Answer:

The atmosphere is divided into various layers that lie on one another and exert pressure on the layer lying below it. They are as follows:

1. Troposphere: It is the lowest layer of the Earth's surface that extends to a height of 8 km at the poles and 18 km at the Equator. This layer is characterised with weather phenomenon like cloud formation, thunderstorms, rainfall and snowfall. Here, temperature decreases with the increase in height.

2. Stratosphere: This layer extends to a height of 50 km from the surface. Temperature increases with increase in height, and this layer is comparatively calm, making the conditions favourable for the movement of aircraft. Here, the presence of ozone layer is witnessed, which protects the Earth from harmful ultraviolet rays.

3. Mesosphere: This layer extends to a height of around 80 km from the Earth's surface. Here, the temperature starts decreasing with the increasing height.

4. Thermosphere: In this layer of atmosphere, the electrically charged ions are present that reflects the radio waves back to the Earth making the communication process possible on the Earth. This layer extends up to a height of around 450 km. It is also known as ionosphere.

5. Exosphere: This layer extends to a height of around 1,600 km and beyond that, it merges with the interplanetary space.

The layers can be understood with the help of below mentioned diagram:

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Question D.3:

How is the atmosphere useful to us?

Answer:

The usefulness of the atmosphere can be understood with the below mentioned points:
  • The components of atmosphere have a great utility. For example, nitrogen, the most important component of the atmosphere, is needed for the growth of plants and for the fertility of soil.
  • Oxygen is a life-giving gas, which is the pre-requisite for human life on the Earth.
  • Carbon dioxide is needed by plants to make their own food. It also helps in maintaining the temperature of the Earth's surface by absorbing the heat radiated from the Earth surface.
  • The water vapour present in the atmosphere helps in bringing rainfall on Earth.
  • Ozone layer protects the Earth from harmful ultraviolet rays emitted from the Sun.
  • Even the dust particles are useful to us since they act as the base during condensation to form water droplets.
 

Page No 28:

Question E.1:

The lowest layer of the atmosphere is

a. mesosphere
b. stratosphere
c. troposphere
d. thermosphere

Answer:

The correct answer is option (c).

Explanation: Troposphere is the lowest layer of the Earth's atmosphere extending to a height of 8 kilometres at the poles and 18 kilometres at the Equator.

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Question E.2:

The uppermost layer of the atmosphere is

a. troposphere
b. exosphere
c. mesosphere
d. ionosphere

Answer:

The correct answer is option (b).

Explanation: This layer extends to a height of around 1,600 kilometres and it further merges with the outer space making it difficult to know much about the layer.

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Question E.3:

The approximate height of the atmosphere is

a. 1200 km
b. 1400 km
c. 1500 km
d. 1600 km

Answer:

The correct option is (d).

Explanation: The uppermost layer of the Earth's atmosphere, that is, the exosphere extends up to a height of 1,600 km and beyond this point, the atmosphere merges with the interplanetary space.

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Question E.4:

All weather phenomena take place in the

a. troposphere
b. stratosphere
c. mesosphere
d. thermosphere

Answer:

The correct answer is option (a).

Explanation: Troposphere is the lowest layer of the Earth's atmosphere where all weather phenomena like formation of clouds, thunderstorms, rainfall and snowfall occur.



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