Ans: C

Exp:

Statement 1 is incorrect: Water vapour is an important component of the atmosphere. The temperatures decrease from the equator to the poles, and as the temperatures decrease, the air becomes cooler. Cooler air has a lower capacity to hold moisture, leading to a decrease in the percentage of water vapour in the atmosphere.

Statement 2 is incorrect: The concentration of dust particles is higher in the subtropical and temperate regions due to dry winds in comparison to the equatorial and polar regions. Dust particles are generally concentrated in the lower layers of the atmosphere, but convectional air currents may transport them to greater heights.

Reference: Chapter 8, Composition and Structure of Atmosphere, Fundamentals of Physical Geography.

Ans: A

Exp

Statement 1 is incorrect: Carbon dioxide is transparent to the incoming solar radiation (insolation) but opaque to the outgoing terrestrial radiation. It absorbs some terrestrial radiation and reflects some of it towards the earth’s surface. It is largely responsible for the greenhouse effect.

Statement 2 is correct: Ozone acts as a filter and absorbs the ultraviolet rays radiating from the sun, preventing them from reaching the surface of the earth. When the ozone layer depletes, more UV light reaches Earth, increasing its temperature. Ozone is a gas made up of three oxygen atoms (O3). It occurs naturally in small amounts in the stratosphere. Ozone protects life on Earth from the Sun’s ultraviolet (UV) radiation. In the troposphere, ozone is created by chemical reactions between air pollutants from vehicle exhaust, gasoline vapours, and other emissions. At ground level, high concentrations of ozone are toxic to people and plants.

Statement 3 is correct: Dust, pollen, salt particles, and aerosols are fine particles suspended in the atmosphere. They act as hygroscopic nuclei/condensation nuclei around which water vapour condenses to produce clouds.  When the weight of the nucleus and its condensate becomes too heavy, it falls in the form of precipitation.

Reference: Chapter 8, Composition and Structure of Atmosphere, Fundamentals of Physical Geography.

Ans: B

Exp:

Pair 1 is incorrect: The Ionosphere contains electrically charged particles known as ions. Radio waves transmitted from the earth are reflected back to the earth by this layer, and temperature starts increasing with height in this layer. The ionosphere is a very active part of the atmosphere, and it grows and shrinks depending on the energy it absorbs from the Sun. The name ionosphere comes from the fact that gases in these layers are excited by solar radiation to form ions, which have an electrical charge.

Pair 2 is incorrect: The Troposphere is the lowest layer of the atmosphere. Its average height is 13 km, and it extends roughly to a height of 8 km near the poles and about 18 km at the equator. It is the zone where almost all weather phenomena like rain, fog, etc. are confined.

Pair 3 is correct:  The uppermost layer of the atmosphere above the thermosphere is known as the Exosphere. Very little is known about it, and whatever contents are there, they are extremely rarefied in this layer. The exosphere gradually fades into outer space; therefore, there is no clear upper boundary of this layer.

Pair 4 is correct: The Stratosphere is found above the tropopause and extends up to a height of 50 km. One important feature of the stratosphere is that it contains the ozone layer. This layer absorbs ultraviolet radiation and shields life on Earth from this intense, harmful form of energy.

Reference: Chapter 8, Composition and Structure of Atmosphere, Fundamentals of Physical Geography.

Ans: A

Exp:

The Troposphere is the lowermost layer of the atmosphere. The troposphere contains three-quarters of the mass of the entire atmosphere. The air here is 78% nitrogen and 21% oxygen. The last 1% is made of argon, water vapour, and carbon dioxide. Its thickness is greatest at the equator because heat is transported to great heights by strong convectional currents. This layer contains dust particles and water vapour. All changes in climate and weather take place in this layer. The temperature in this layer decreases at a rate of 1 degree celsius  for every 165m of height. The troposphere is marked by temperature inversions, turbulence, etc. This is the most important layer for all biological activity. 

The temperature is nearly constant in the tropopause (not the troposphere). 

Ionosphere is the layer that influences radio communication and navigation. The ionosphere is located between 80 and 400 km above the mesopause. It contains electrically charged particles known as ions. Because it is  formed when particles are ionized by the Sun’s energy, the ionosphere changes from Earth’s day side to night side. When night falls, the ionosphere thins out as previously ionized particles relax and recombine back into neutral particles. 

Reference: Chapter 8, Composition and Structure of Atmosphere, Fundamentals of Physical Geography.

https://solarsystem.nasa.gov/news/1127/10-things-to-know-about-the-ionosphere/

Ans: D

Exp:

The layers of the atmosphere in descending order are:

• Exosphere: The Exosphere is the outermost part of the atmosphere, located above the thermosphere. Exosphere is derived from the Greek word ‘exo’ meaning outer or external. This is the highest layer, and very little is known about it. The contents present in the exosphere are extremely rare. The exosphere gradually merges with outer space.
• Thermosphere: It is the layer that is located above the mesosphere and below the exosphere. In the thermosphere, temperature rises very rapidly with increasing height.  The ionosphere is a part of this layer. This layer reflects radio waves that are transmitted from the Earth back to the planet. The thermosphere is home to the International Space Station as it orbits Earth. The low Earth orbit satellites can be found in this layer.
• Mesosphere: The third layer of the atmosphere from the earth’s surface is called the mesosphere. It contains the region above the stratosphere and below the thermosphere. Meso” means middle, and in this layer of the atmosphere, the gases are all mixed up rather than being layered by their mass. The meteors make it through the exosphere and thermosphere without much trouble because those layers don’t have much air. But when they hit the mesosphere, there are enough gases to cause friction and create heat. That is why meteors burn in the mesosphere.
• Stratosphere: The second layer of the atmosphere from the earth’s surface is called the stratosphere. “Strat” means layer. This layer of our atmosphere has its own set of layers. There are no storms or turbulence here to mix up the air, so cold, heavy air is at the bottom, and warm, light air is at the top. The ozone layer is found in this layer, and this layer helps protect us from ultraviolet radiation (UV) from the sun. 
• Troposphere: The innermost, lowest layer of the earth’s atmosphere is called the Troposphere. Tropos” means change. This layer gets its name from the weather that is constantly changing and mixing up the gases in this part of our atmosphere. The thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents. It is thinnest at the North and South poles

Reference: Chapter 8, Composition and Structure of Atmosphere, Fundamentals of Physical Geography.

spaceplace.nasa.gov, Mesosphere | NASA Space Place – NASA Science for Kids