. The atmosphere is a mixture of several gases. Near the earth surface it contains mainly:
Correct Answer:
(A) Nitrogen and oxygen
The atmosphere is a mixture of different gases, of which 99% are mainly Nitrogen (78.08%) and Oxygen (20.95%). Remaining approximately 1% are Argon, Carbon dioxide, Neon, Helium, Methane, Hydrogen, Nitrous Oxide, Ozone, Krypton, Xenon, etc. Heavy gases are found at the bottom of atmosphere and light gases are found at the top. Carbon dioxide is found up to 20 km above Earth, Oxygen and nitrogen up to 100 km, Hydrogen up to 125 km and except Ozone other gases are found at much higher elevation.
Ques: 2
The correct sequence of different layers of the atmosphere from the surface of the Earth upwards is:
Correct Answer:
(C) Troposphere, Stratosphere, Mesosphere, Ionosphere
On the basis of temperature and air pressure atmosphere is divided into five layers starting from the earth’s surface which are as follows:
Troposphere- (15 km from the surface of the earth)
Stratosphere (15-50 km)
Mesosphere (50-80 km)
Ionosphere (80-640 km)
Exosphere (above more than 640 km)
So, option (c) is correct.
Ques: 3
In the vertical structure of the atmosphere, which one is the lowest layer?
Correct Answer:
(C) Troposphere
In the Vertical structure of the atmosphere, Troposphere is the lower most layer. Its average elevation is about 15 kms. All seasonal phenomena - like rain, fog, hail, etc. occur on this surface.
Ques: 4
Most weather activity occurs in which atmospheric layer:
Correct Answer:
(C) Troposphere
Almost all the weather phenomena like rainfall, fog and hailstorm, etc. occur in the troposphere. The temperature in this layer decreases at the rate of 6.5°C for every 1000-meter (1 km) height. This is the most important layer for all biological activity.
Ques: 5
The stratosphere is said to be ideal for flying jet aircraft. This is because-
Correct Answer:
(D)
The absence of clouds and other weather phenomena
The stratosphere is the second major layer of Earth’s atmosphere, just above the troposphere, and below the mesosphere. The stratosphere is very dry and air of this layer contains little water vapour. Because of this, Stratosphere is almost free from clouds and associated weather phenomenon. These conditions are ideal in order to avoid disturbances. Jet aircraft use to fly in this layer.
Ques: 6
The ozone layer lies in the:
Correct Answer:
(C) Stratosphere
The ozone layer is mainly found in the lower portion of the stratosphere from 15 to 35 kilometres above Earth. The maximum height of this layer is 55 kilometres but the concentration of ozone layer is found from 15 to 35 kilometre. This layer absorbs ultra-violet radiation and shields life on the Earth from an intense and harmful form of energy. Ultra-violet rays may cause skin cancer.
Ques: 7
Which of the following protects life on earth from the harmful radiations of the Sun?
Correct Answer:
(C) Ozone layer
The ozone layer protects us from the harmful radiations of the Sun. In atmosphere, it is mainly found in the lower portion of the Stratosphere from 15–35 km above Earth. Ozone is a molecule composed of three oxygen atoms. Its colour is blue.
Ques: 8
Which one of the following layers of the atmosphere is responsible for the deflection of radio waves?
Correct Answer:
(D)
Ionosphere
Radio waves are reflected by the Ionosphere. Other major events that occur in this region are as follows- Identification of cosmic rays and observation of Aurora Borealis and Aurora Australis.
Ques: 9
Which layer of atmosphere is responsible for Aurora Borealis?
Correct Answer:
(B) Thermosphere
Aurora is an incredible light caused by collisions between electrically charged particles released from the Sun that enter the Earth atmosphere. Aurora that occurs in the Northern Hemisphere is called 'Aurora Borealis' and in Southern Hemisphere is called 'Aurora Australis'. The light of Aurora extends from (80 Km to 640 Km).
The thermosphere is where the aurora (Southern and Northern Lights) occur. At high latitudes, charged particles from space clash with atoms and molecules in the thermosphere, causing them to be excited into higher energy levels. These atoms and molecules release their surplus energy by producing light photons, which we perceive as vivid auroral displays.
Ques: 10
Wireless communication is reflected to the earth’s surface by –
Correct Answer:
(C) Ionosphere
The Ionosphere is composed of electrically charged particles that are called ‘ions’. These particles reflect radio waves back to the Earth surface and enable us to have wireless communication.
Ques: 11
In which atmospheric layer are communication satellites located?
Correct Answer:
(A) Exosphere
Geostationary satellites are positioned at approximately 36000 km height above the Earth. Exosphere is the outer limit of the atmosphere above 640 km from the Earth. Therefore, the communication satellite located in outer most layer of the atmosphere are in Exosphere.
Ques: 12
Which of the following are correct in matching the layer of atmosphere and its characteristics?
Troposphere – Weather Phenomena
Stratosphere – Ozone layer
Ionosphere – Radio waves reflected to Earth's surface
Mesosphere – Aurorae
Code:
Correct Answer:
(C) 1, 2, and 3
Almost all the weather phenomena like rainfall, fog and hailstorm etc. occur in troposphere. Stratosphere - contains a layer of ozone gas. Radio waves transmitted from the earth are reflected back to the Earth by Ionosphere. Auroras are also related to this layer. So, option 1, 2 and 3 are correctly matched, while option (4) is incorrect.
Ques: 13
Given below are two statements, one is labelled as Assertion (A) and other as Reason (R) :
Assertion (A): The atmosphere receives most of the heat only indirectly from the sun and directly from the earth’s surface.
Reason (R): The conversion from shortwave solar to long wave terrestrial energy takes place at the earth’s surface.
Code:
(A) and (R) are true, and (R) is the correct explanation of
(A).
Correct Answer:
(A) and (R) are true, but (R) is not the correct explanation of
The principal source of atmospheric and Earth’s surface energy is the Sun. Insolation is the incoming solar Energy intercepted by the Earth. The energy radiated from the Sun is known as short-wave solar radiation whereas the energy radiated from Earth is known as long-wave radiation. The long-wave radiation is absorbed by the atmospheric gases particularly by carbon dioxide and the other green- house gases. Thus, the atmosphere is indirectly heated by the Earth’s radiation. Increasing concentration of greenhouse gases such as carbon dioxide and methane increases the temperature of the lower atmosphere by restricting the outward passage of emitted radiation, resulting in global warming.
Ques: 14
Normally, the temperature decreases with the increase in height from the Earth’s surface, because
The atmosphere can be heated upwards only from the Earth’s surface.
There is more moisture in the upper atmosphere.
The air is less dense in the upper atmosphere.
Select the correct answer using the codes given below:
Correct Answer:
(C) 1 and 3
Globally, insolation is the main factor behind the distribution of temperature. By absorbing Sunrays, the surface of Earth gets warmer. This is the reason why temperature decreases as height increases. At high altitude air density is less with little humidity. Hence, statement (1) and (3) are correct while (2) is wrong. Therefore, option (c) is the correct answer.