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

(b) exosphere

Step 1: Understanding the Atmosphere Layers

The atmosphere is divided into several layers based on temperature gradients. These layers are: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

Step 2: Identify the Highest Layer

The question asks for the upper most region of the atmosphere. The exosphere is the outermost layer of the atmosphere, extending from the top of the thermosphere up to 10,000 km above the Earth's surface.

Step 3: Compare the Options

Given the options: (a) troposphere, (b) exosphere, (c) stratosphere, and (d) ionosphere, we see that the exosphere is the highest layer listed.

Key Concepts

Troposphere

The troposphere is the lowest layer of Earth's atmosphere. This is where all life on Earth exists and where nearly all weather conditions occur. It extends from the Earth's surface up to about 8 to 15 kilometers high, depending on your location from the equator to the poles.
The air we breathe, clouds, rain, and storms all take place in this layer. The troposphere's temperature decreases with altitude, which means it gets colder the higher you go.
Key points about the troposphere include:

• Contains about 75% of the atmosphere's total mass.
• Holds most of the world's weather systems.
• Temperature decreases as you ascend.
• It has a boundary on top known as the tropopause, which separates it from the stratosphere.

Due to these features, the troposphere plays a crucial role in Earth's climate and weather patterns.

Exosphere

The exosphere is the outermost layer of Earth's atmosphere. It begins about 600 kilometers above the Earth and extends outwards to about 10,000 kilometers.
This layer is very thin and gradually fades into outer space, meaning it consists mainly of hydrogen and helium particles dispersed widely. The air is so sparse that there's no clear upper boundary leading into space.
Important aspects of the exosphere include:

• It is where satellites orbit the Earth.
• Contains light gases like hydrogen and helium.
• The air particles are so few that they can travel hundreds of kilometers before colliding with one another.
• There is little to no air pressure.

This layer marks the transition from Earth's atmosphere into outer space, showcasing phenomena that are drastically different from those near the Earth's surface.

Stratosphere

The stratosphere is positioned above the troposphere and below the mesosphere, spanning from about 15 to 50 kilometers above the Earth's surface. Unlike the troposphere, the temperature in the stratosphere increases with altitude.
It is home to the ozone layer, which absorbs and scatters ultraviolet solar radiation, playing a vital role in protecting life on Earth.
Characteristics of the stratosphere include:

• Hosts the ozone layer, which is crucial for absorbing harmful UV radiation.
• Has a stratified temperature profile, as temperatures increase with height.
• A more stable air system, meaning it lacks the weather activities found in the troposphere.
• Jet aircraft often fly in the lower stratosphere to avoid the weather turbulence of the troposphere.

The stratosphere is essential for maintaining the thermal balance and protecting living organisms from ultraviolet radiation.