Problem 13 - A Complete Resource Book in Chemistry for JEE Main

Question

The upper most region of the atmosphere is (a) troposphere (b) exosphere (c) stratosphere (d) ionosphere

Step-by-Step Solution

Answer

The upper most region of the atmosphere is the exosphere (b).

Step 1: Identify the Layers of the Atmosphere

The atmosphere is composed of several layers, each distinguished by its characteristic temperature profile and composition. From the surface of the Earth upwards, these layers are the Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.

Step 2: Define the Upper Most Layer

Among the layers identified, the Exosphere is considered the outermost or 'upper most' region of the Earth's atmosphere. It gradually fades into outer space.

Step 3: Match the Options

Compare the given options with the defined layers of the atmosphere: (a) Troposphere - lowest layer, (b) Exosphere - upper most layer, (c) Stratosphere - second layer, (d) Ionosphere - a region composed of parts of the Mesosphere, Thermosphere, and Exosphere.

Step 4: Choose the Correct Answer

Based on the comparison and definitions, option (b) Exosphere is the correct answer as it represents the upper most region of the atmosphere.

Key Concepts

Troposphere

The troposphere is the lowest layer of Earth's atmosphere and where we live our daily lives. It's also where all weather changes occur, such as snow, rain, and clouds. The height of the troposphere varies, being higher at the equator and lower at the poles.

• This layer extends up to about 8 to 15 kilometers (5 to 9 miles) above the Earth's surface.
• Temperature drops with altitude, meaning it gets colder as you go higher.
• The troposphere comprises around 75% of Earth's atmosphere's mass.
• It contains water vapor, important for weather patterns and climate.

Planes usually fly in the upper parts of the troposphere to avoid turbulence caused by weather activities.

Exosphere

The exosphere is the outermost layer of Earth's atmosphere, gradually transitioning into the vacuum of outer space. This layer is where the atmosphere thins out and molecules drift away into space. It's a fascinating layer primarily because of how it interacts with the solar wind.

• The exosphere starts at about 700 kilometers (435 miles) above Earth and extends out to about 10,000 kilometers (6,200 miles).
• This region is mostly composed of light gases like hydrogen and helium.
• Molecules in the exosphere move incredibly fast and can escape Earth's gravity.
• Satellites often orbit within this layer as there's minimal drag from atmospheric gases.

While it might seem empty, the exosphere plays a crucial role in protecting Earth from cosmic and solar radiation.

Stratosphere

Located above the troposphere, the stratosphere extends from about 15 to 50 kilometers (9 to 31 miles) above Earth's surface. This layer is of great interest for both science and aviation due to its stability and unique properties.

• The stratosphere is where the ozone layer is located, which absorbs and scatters ultraviolet solar radiation.
• Unlike the troposphere, temperatures in the stratosphere increase with height due to this absorption of UV rays by ozone.
• With its calm conditions, it provides an ideal environment for high-altitude research and military aircraft.
• Commercial jets often fly at the lower edge of this layer to avoid turbulence and benefit from increased fuel efficiency.

Understanding the stratosphere is vital because it significantly impacts Earth's climate and radiation balance.

Ionosphere

The ionosphere is not a distinct layer like the others but rather a region of the upper atmosphere, extending from about 60 kilometers (37 miles) to 1,000 kilometers (620 miles) above Earth. It overlaps with parts of the mesosphere, thermosphere, and exosphere.

• This region is ionized by solar radiation, meaning it contains charged particles.
• The ionosphere is crucial for radio communications, as it reflects and modifies radio waves used for transmitting signals over long distances.
• It is also where phenomena like the Aurora Borealis (Northern Lights) and Aurora Australis (Southern Lights) occur.
• Daily and seasonal changes affect the density and composition of the ionosphere.

By studying the ionosphere, scientists can improve communication systems and understand space weather's effects on our technology.