Question 1:
Which one of the following gases constitutes the major portion of the atmosphere?
- Oxygen
- Nitrogen
- Argon
- Carbon dioxide
Answer:
(b). Nitrogen
Question 2:
Atmospheric layer important for human beings is:
- Stratosphere
- Mesosphere
- Troposphere
- Ionosphere
Answer:
(c). Troposphere
Question 3:
Sea salt, pollen, ash, smoke soot, fine soil—these are associated with:
- Gases
- Dust particles
- Water vapour
- Meteors
Answer:
(b). Dust particle
Question 4:
Oxygen gas is in negligible quantity at the height of atmosphere:
- 90 km
- 120 km
- 100 km
- 150 km
Answer:
(b). 120 km
Question 5:
Which one of the following gases is transparent to incoming solar radiation and opaque to outgoing terrestrial radiation?
- Oxygen
- Nitrogen
- Helium
- Carbon dioxide
Answer:
(d). Carbon dioxide
Question 6:
What do you understand by atmosphere?
Answer:
Atmosphere is a vast expanse of air which envelopes the earth all around. It represents the gaseous realm of the earth. It is held to the earth by the force of gravity. It is, thus, an integral part of the earth. It is a very vital part of human existence on the earth.
Question 7:
What are the elements of weather and climate?
Answer:
The atmospheric conditions which make up the
weather of place are known as elements of weather. These
are :
(a) Temperature
(b) Pressure
(c) Winds
(d) Sun- shine
(e) Humidity
(f) Cloudiness
(g) Rainfall
(h) Mist and fog.
The major controls of climate :
The factors which change the climate from place to
place are known as the elements of climate.
(a) Latitude
(b) Altitude
(c) Distribution of land and water
(d) pressure
(e) Prevailing winds
(f) Ocean currents
(g) Mountain barriers.
Question 8:
Why is the troposphere the most important of all the layers of the atmosphere?
Answer:
Of all the layers of the atmosphere,
troposphere is the most important in climatology due
to the following reasons :
(a) This is the weather maing layer of the
atmosphere.
(b) All the weather making processes are confined
to this layer.
(c) Great contrasts in climate and weather are
observed in different areas due to changes of
temperature in this layer.
(d) The presence of most of the water vapour in
this layer is responsible for condensation, clouds and
precipitation.
(e) Dust particles give rise to fog, clouds, smog, etc.
in this layer.
(f) Convection currents are confined to this layer for
the heating and cooling of the atmosphere.
Question 9:
Describe the composition of the atmosphere.
Answer:
The atmosphere mainly consists of a mixture
of gases in a fairly constant composition. The
atmosphere is composed of following three elements :
1. Gases. Nitrogen and Oxygen are the two major
gases found in the atmosphere. Nitrogen occupies 78%
and Oxygen occupies 21% by volume. The remaining
1% is composed of a number of gases like Hydrogen,
Argon, Ozone, Helium, Carbon dioxide. The
proportions of the gases remain constant. Oxygen is
the most vital gas for sustaining life. Nitrogen and
Carbon dioxide are essential for plant life. Oxygen
will be negligible at the height of 120 km. Carbon
dioxide and water vapour are found upto 90 km.
The gases present in the atmosphere are :
Nitrogen 78.08%
Oxygen 20.95%
Argon 0.93%
Carbon dioxide 0.03%
Hydrogen and Other gases 0.01%
Total 100%
2. Water Vapour. The amount of water vapour
varies from place to place and time to time. Water
vapour represents 2% of the air by volume. It is mostly
found in the lower layers of the troposphere. About
half the water vapour in the air lies below an altitude
of 2000 metres. The maximum amount of water
vapour is found between 10° and 30° latitudes. It is
of primary importance to man. It absorbs insolation.
It is the source of all condensation and precipitation
on the earth. Water vapour decreases from the equator
towards the poles. It is less than 1% in polar area,
dry and cold areas of deserts. It preserves the earth
radiation and acts as a blanket. It contributes to
stability and instability of the air.
3. Dust Particles. The atmosphere holds in
suspension many dust particles whose size varies. The
major source of dust particles are deserts, lake beds,
beaches and dry river beds. These are found in the
lower layers of the atmosphere. These affect sun-rays
by scattering and absorbing insolation. These are
responsible for the formation of clouds, fog and smog.
Dust particles act as Hygroscopic nuclei for clouds.
These include sea salts, fine soil, smoke soot, ash,
pollen, dust, and particles of meteors.
Question 10:
Draw a suitable diagram for the structure of the atmosphere and label it and describe it.
Answer:
Atmosphere. Atmosphere is a vast expanse
of air which envelopes the earth all around. It
represents the gaseous realm of the earth. The
atmosphere consists of different layers. With the
increase in altitude, the atmospheric pressure, density
and temperature goes on decreasing. Therefore, on the
basis of temperature and density, the atmosphere can
be divided into five basic layers.
1. Troposphere : It is the lowest layer of the
atmosphere. Its average height is sixteen kms. Most
of the clouds, water vapours, dust particles and
atmospheric disturbances are found in this layer. The
upper boundary of troposphere is called the
Tropopause. The temperature decreases at the ratio
of 1°C per 165 metres (normal lapse rate).
This layer is important for mankind because it is
the weather making layer. Convection currents are
confined to this layer. The air is unstable in this zone.
This is sometimes called ‘unstable zone.’ Its height is
8 kms near the poles and 18 kms near the equator
(average 13 kms).
2. Tropopause : The upper boundary of
troposphere is called tropopause. This layer starts
where troposphere ends. Above this, stratosphere
starts. It is a zone about 1½ km broad. In this
transitional zone, the wind and convection currents
are absent and the temperature is constant. The air
temperature at the tropopause is – 80°C at the equator
and – 45°C over the poles.
3. Stratosphere : This layer lies next to the
troposphere. Its average height is 60 kms. It is free
from clouds, dust particles, water vapour and
convection currents. The temperatures are very low
and fairly constant. Its height is higher at the equator
than at the poles. Its height is higher in summer than
in winter. By the observations from Sputnik, its height
has been estimated between 16 to 80 kms. In this
zone, the temperature does not increase with altitude.
On the other hand the temperature remains constant.
The air temperature is – 80°C over the equator and –
45°C over the poles.
4. Ozonosphere : Due to concentration of ozone
gas it is called ozonosphere. It absorbs ultra violet
rays of the sun. It has high temperature due to
absorption of these rays. Without the layer of ozone
gas, human existence on earth would not have been
possible. People would have become blind and their
bodies would have been burnt due to ultra violet rays.
It is a very hot zone because the temperature
increases at the rate of 16°C per km with altitude. It
has been observed that this layer is decreasing over
Antarctica.
5. Mesosphere : Mesosphere lies above the
stratosphere and extends upto a height of 80 km.
Temperature starts increasing with altitude and
reaches – 100°C at height of 80 km. The upper limit
is called Mesosphere.
6. Ionosphere : It lies between 60 to 400 km above
the Mesosphere. It contains electrically charged
particles called ions. Radio waves transmitted from
the earth are reflected back to the earth by this layer.
Temperature starts increasing.
7. Exosphere : The upper most layer of the
atmosphere above ionosphere is called Exosphere.
Very little is known about it. It gradually merges with
outer space.