Composition and Structure of Atmosphere For Class 11 Geography Test Paper

Ans. (b) Nitrogen

Ans. (c) Ozone

Ans. (d) burning of fossil fuels

Ans. (b) Pressure

Ans. (c) Carbon dioxide

Ans. (a) Earth’s temperature to rise

Ans. (b) oxygen

Ans. (b) Earth

Ans. (c) Atmosphere

Ans. (b) exosphere

Ans. (d) all of them

Ans. (b) Tropopause

Ans. (b) 78.08%

Ans. (a) 120 km.

Ans. (b) 99

Ans. (c) nitrogen

Ans. (a) 0.036%

Ans. (d) xenon

Ans. (b) carbon dioxide

Ans. (b) water vapour

Ans. (c) ozone

Ans. (b) troposphere

Ans. (a) 20.95

Ans. (b) mesopause

Ans. (a) tropopause

Ans. (c) ionosphere

Ans. (b) stratosphere

Ans. (a) troposphere

Ans. (a) 80 and 400 km.

Ans. (c) 50 km.

Ans. The water vapour and dust particles are important variables of weather and climate because they are the source of all forms of condensation and principal absorbers of heat received from the sun or radiated from the earth. Besides, they affect the stability of the atmosphere.

Ans. The temperature decreases with altitude because the atmosphere is heated more by the heat radiated from the earth’s surface. Wanner air lying under the cooler air goes up or turns downward. In this layer, the temperature decreases vertically at a rate of 0.65°C per 100 metres. It is called the normal lapse rate

Ans. The atmospheric layer up to an altitude of 90 km. above the surface of the earth is generally called homosphere. It is uniform in term of these major gases – nitrogen, oxygen and argon. In addition, it also contains some rare gases like neon, krypton and xenon.

Ans. Nitrogen, oxygen and argon are the most important gases of the atmosphere. In addition, it contains gases like carbon dioxide, neon, helium, ozone, hydrogen, methane, krypton and xenon. Besides, there are also present huge amounts of solid and liquid particles collectively called aerosols.

Ans. Nitrogen is the most abundant gas of the atmosphere. By volume, it constitutes 78.8% of the total gases present in the atmosphere. Nitrogen does not easily enter into chemical union with other substances but gets fixed into the soil. It serves mainly as diluent or dissolver. It regulates combustion.

Ans. By volume carbon dioxide constitutes 0.03% of the total gases of the earth’s atmosphere. Although it forms a small portion, it is an important gas in the atmospheric processes. It can absorb the heat and thus allows the lower atmosphere to be warmed up by heat radiation coming from the sun and from the earth’s surface. Green plants in the process of photosynthesis utilise carbon dioxide from the atmosphere.

Ans. The earth is the only known planet to have life. The atmosphere, which is unlike that of any other planet, encircles and protects the earth. Changes in the composition of the atmosphere are closely associated with the evolution of the earth. One of the most important transition was the increase in oxygen when photosynthetic plants evolved.

The atmosphere is a mixture of gases, the largest proportion of which is nitrogen. However, the most important is oxygen, without which life could not be sustained. The very survival of life processes is associated with the atmosphere.

The influence of the atmosphere on humans particularly is not only direct but also indirect through natural vegetation, soil and topography.

Ans. Condensation is the physical process of the transition of a substance from the vapour to the liquid state, e.g., as a result of cooling or increase of pressure. It occurs in the atmosphere when the air is saturated or when it is cool. Thus, the change of state of the moisture from invisible water vapour to visible liquid (water) or solid (ice or snow ) state is known n as condensation. It is opposite of evaporation.

Precipitation, on the other hand, means ‘throwing down of moisture’. Continuous condensation in the body of the air helps the water droplets to grow in size so that the resistance of the air fails to keep them suspended. In such cases, only an ascending air current can keep them floating in the air. In the absence of such a current, the products of condensation begin to fall on the earth’s surface. The process whereby the water vapour first condenses in the air and then falls on to the earth is called precipitation.

Ans. Three major features are :

• It is 16 km thick at the equator and 10 km thick at the poles.
• The temperature decreases with the altitude at the rate of 1°C per 165 metres.
• Biological activities take place in this layer.