Problem 58 - A Complete Resource Book in Chemistry for JEE Main

Question

An object is located at a height of \(5 \mathrm{~km}\) from the surface of the earth. The object is located in which part of atmosphere? (a) thermosphere (b) mesosphere (c) stratosphere (d) troposphere

Step-by-Step Solution

Answer

The object is in the troposphere.

Step 1: Understanding the Layers of the Atmosphere

The Earth's atmosphere is broadly divided into four main layers: the troposphere, stratosphere, mesosphere, and thermosphere. Each layer has distinct characteristics and occupies a specific range of altitudes above the Earth's surface.

Step 2: Identifying the Altitude Range for Each Layer

1. **Troposphere**: This layer extends from the Earth's surface up to about 8-15 km. It is where most weather phenomena occur. 2. **Stratosphere**: Ranges from approximately 15 km to 50 km. This layer contains the ozone layer. 3. **Mesosphere**: Extends from 50 km to around 85 km. 4. **Thermosphere**: Starts above 85 km and extends up to about 600 km.

Step 3: Locating the Given Altitude

The object is located at a height of 5 km. We compare this height with the altitude ranges for the different atmospheric layers.

Step 4: Choosing the Correct Layer

Since 5 km falls within the 0-15 km range, which corresponds to the troposphere, the object is located in the troposphere.

Key Concepts

troposphere

The troposphere is the lowest layer of Earth's atmosphere. It begins at the Earth's surface and extends upward to about 8-15 kilometers. This variation depends on the latitude, being thicker at the equator and thinner at the poles. The troposphere is where we live, and it contains most of the mass of the atmosphere. It is essential for weather activity, as it is in this region that clouds form, and almost all of our weather occurs.
The temperature in the troposphere decreases with altitude. This is why it's colder at the top of a mountain than it is at the base.

• The troposphere contains approximately 75% of the atmosphere's mass and 99% of the water vapor and aerosols.
• Air pressure and density decrease with altitude in this layer.
• Its boundary, the tropopause, separates it from the stratosphere above.

Understanding the troposphere is crucial because of its direct impact on the climate and weather patterns that affect our daily lives.

stratosphere

Above the troposphere lies the stratosphere, extending from about 15 km to 50 km above Earth's surface. One of the most notable features of the stratosphere is the ozone layer, which absorbs and scatters ultraviolet solar radiation, protecting life on Earth.
In contrast to the troposphere, the temperature in the stratosphere increases with altitude. This is because of the absorption of ultraviolet radiation by ozone, which heats the layer.

• The stratosphere lacks the turbulent air and weather phenomena seen in the troposphere, resulting in relatively stable air conditions.
• Jets and balloons often reach their maximum altitudes in the lower stratosphere, where the air is thinner, and there is less air resistance.
• This layer acts as a protective shield against the sun's harmful rays.

Overall, the stratosphere plays a vital role in maintaining balance in Earth's atmospheric conditions.

mesosphere

The mesosphere is located above the stratosphere, ranging from about 50 km to 85 km above the Earth’s surface. It is the coldest part of the atmosphere, with temperatures decreasing as you go higher.
The mesosphere is best known for being the region where most meteors burn up upon entry due to friction with atmospheric particles.

• This layer has very little water vapor; thus, there is little potential for cloud formation.
• It is too high for aircraft but too low for satellites, making it one of the least understood layers of the atmosphere.
• Unique types of clouds, called noctilucent clouds, can sometimes form in this layer.

Despite being less explored, the mesosphere offers fascinating phenomena such as "sprites" and "elves," which are types of upper-atmospheric lightning.

thermosphere

The thermosphere starts above the mesosphere and extends up to around 600 km above Earth. This layer is characterized by increasing temperatures with altitude, particularly during the daytime, as it absorbs the sun’s extreme ultraviolet and X-ray radiation.
The thermosphere is where the International Space Station orbits and where auroras occur.

• It has very low air density, resulting in negligible resistance to spacecraft.
• Temperatures can soar to 2,500 degrees Celsius or higher, yet it feels cold to our skin due to low pressure.
• The thermosphere's upper boundary, known as the thermopause, marks the transition to the exosphere.

This layer's temperature variations are vital for transmitting radio waves, making it essential for communication purposes.