Test: Composition & Structure Of Atmosphere - 2 - UPSC MCQ

The air pressure at the sea level is found to be 760 mm Hg. This is also equal to 101.325 kilopascals.

Although monsoons are often erroneously identified as rainstorms, they are actually a seasonal wind. A monsoon is a wind in low-latitude climates that seasonally changes direction between winter and summer.

In the northern hemisphere, south-facing slopes are warmest because the sun stays mostly in the southern half of the sky.

The ozone layer is primarily found in the Stratosphere. This layer of the Earth's atmosphere contains a high concentration of ozone (O₃) molecules, which play a crucial role in absorbing and scattering the solar ultraviolet radiation, protecting living organisms from harmful UV rays.

By volume, dry air contains approximately 0.93% argon. Argon is the third most abundant gas in the Earth's atmosphere after nitrogen and oxygen.

The chief elements of the atmosphere include various physical factors that characterize its state and behavior. These elements include wind, temperature, and pressure, among others. Each of these factors plays a critical role in defining the meteorological conditions of the atmosphere.
Wind, temperature, and pressure are fundamental atmospheric elements that interact to influence weather patterns, climate conditions, and the general environment of the Earth.

Hail is produced by the rapid ascent of moist air. The hard pellets of ice having diameter of 5 mm or that fall from Cumulonimbus clouds, and are generally associated with thunderstorms is known as hail. They are formed by the rapid ascent of moist air; the water drops freeze, and the size of the pellets increases as more water Vapour freezes on to their surface.

Carbon Dioxide:

• Carbon dioxide is meteorologically a very important gas.
• It is transparent to the incoming solar radiation but opaque to the outgoing terrestrial radiation.
• It absorbs a part of terrestrial radiation and reflects back some part of it towards the earth’s surface.
• It is largely responsible for the greenhouse effect.
• The volume of other gases is constant but the volume of carbon dioxide has been rising in the past few decades mainly because of the burning of fossil fuels.
• This has also increased the temperature of the air.

​Thus, carbon dioxide is transparent to incoming solar radiation and opaque to outgoing terrestrial radiation.

• Atmosphere: The earth is surrounded by a layer of gas called the atmosphere. This thin blanket of air is an integral and important aspect of the planet.
• Gaseous composition of the atmosphere:
  • The air in the atmosphere is a mixture of many gases like nitrogen, oxygen, carbon dioxide, and water vapours.
  • The atmosphere is composed mainly of nitrogen and oxygen
  • Nitrogen and oxygen are two gases that make up the bulk of the atmosphere.
  • Carbon dioxide, helium, ozone, argon, and hydrogen are found in lesser quantities.
  • Nitrogen is the most plentiful gas in the air. It comprises 78% of the total composition of air.
  • Oxygen holding the second position by volume constitutes 21% of the atmosphere.

The atmosphere plays a crucial role in sustaining and protecting life on Earth through several mechanisms:

• The ozone layer (A) absorbs and scatters the majority of the sun's harmful ultraviolet radiation, protecting living organisms from DNA damage and other harmful effects.
• Greenhouse gases (B) like carbon dioxide and methane trap heat in the atmosphere, creating a warmer environment that is suitable for life as we know it. This greenhouse effect increases the average temperature near the Earth's surface, making it habitable.
• Oxygen (C), a major component of the atmosphere, is essential for the respiration of most living organisms and supports the combustion processes that are critical for various human activities.

Answer: D: all of the choices

Each of these aspects contributes significantly to creating and maintaining conditions that support diverse life forms on our planet.

The mesosphere is one of the layers of Earth's atmosphere and is situated above the stratosphere. It extends from about 50 kilometers (31 miles) to 85 kilometers (53 miles) above the Earth's surface. The layer above the mesosphere is the thermosphere.
This positioning makes the mesosphere the third layer of the atmosphere, directly above the stratosphere and below the thermosphere.

The layer of the atmosphere most useful for various biological activities is the troposphere. This is the lowest layer of Earth's atmosphere and extends from the Earth's surface up to about 10 kilometers (6 miles) in altitude. The troposphere contains approximately 75% of the atmosphere's mass and is where almost all weather conditions take place. It is rich in oxygen and nitrogen which are essential for life, and the temperature and pressure conditions are suitable for biological activities.

• Xenon is present in the Earth's atmosphere in trace amounts, around 0.000009% by volume.
• Oxygen and nitrogen are major components of the atmosphere, making up about 21% and 78% respectively.
• Carbon dioxide, though present in small amounts, is still more abundant than xenon at about 0.04%.
• Xenon is a noble gas and is much less common in the atmosphere compared to the other gases listed.

Dust particles include sea salt, pollen, ash, smoke soot, and fine soil, which play a role in cloud formation.

Oxygen is present in very negligible amounts at a height of 120 km from the Earth's surface.