Question

Briefly describe the absorption of solar radiation in the stratosphere by \(\mathrm{O}_{2}\) and \(\mathrm{O}_{3}\) molecules

Short answer

Oxygen absorbs UV-C, forming ozone, which then absorbs UV-B, protecting life on Earth.

Step-by-step solution

Understanding Solar Radiation

Solar radiation primarily consists of ultraviolet (UV), visible, and infrared light. UV light is particularly important in atmospheric chemistry due to its energy.

Absorption by Oxygen ( \(\mathrm{O}_{2} \))

In the upper stratosphere, molecular oxygen (\(\mathrm{O}_{2}\)) absorbs high-energy UV-C radiation (wavelengths less than 242 nm). This process leads to the dissociation of \(\mathrm{O}_{2}\) into individual oxygen atoms.

Formation of Ozone ( \(\mathrm{O}_{3} \))

The free oxygen atoms (\(\mathrm{O}\)) from dissociation collide with other \(\mathrm{O}_{2}\) molecules to form ozone (\(\mathrm{O}_{3}\)). This process is an essential part of the ozone-oxygen cycle.

Absorption by Ozone ( \(\mathrm{O}_{3} \))

Ozone (\(\mathrm{O}_{3}\)) absorbs UV-B and some UV-C radiation (wavelengths between 200-320 nm). This absorption prevents harmful UV radiation from reaching the Earth's surface.

Protective Role of Stratosphere

The absorption of UV radiation by \(\mathrm{O}_{2}\) and \(\mathrm{O}_{3}\) in the stratosphere protects living organisms on Earth by reducing exposure to harmful UV radiation.

Key concepts

Stratosphere

The stratosphere is a crucial layer of the Earth's atmosphere, sitting above the troposphere and below the mesosphere. It extends from about 10 to 50 kilometers above the Earth's surface. This layer is unique because it contains the ozone layer, which plays a critical role in protecting life on Earth. One of the standout features of the stratosphere is its temperature profile; here, temperatures increase with altitude. This is opposite to what occurs in the troposphere, where temperatures usually drop with height. The temperature inversion in the stratosphere results from the absorption of UV radiation by ozone, which heats the air.

Why is the stratosphere important for us? It's essential for several reasons:

• The ozone layer within it absorbs a significant amount of the Sun's ultraviolet radiation, which is harmful to living organisms.
• It acts as a kind of thermal blanket, helping regulate Earth's temperature.
• Due to its stable layers, the air in the stratosphere is less turbulent, which is why large-scale weather occurs primarily below this layer.

Understanding the stratosphere is vital to understanding how solar radiation interacts with our atmosphere!

Ozone Formation

Ozone (\( \mathrm{O}_{3} \)) is a molecule composed of three oxygen atoms. It forms in the stratosphere through processes initiated by the absorption of ultraviolet (UV) light. This formation is a key part of the essential ozone-oxygen cycle.

Here's how ozone is created:

• When high-energy UV-C radiation strikes molecular oxygen (\( \mathrm{O}_{2} \)), it splits the \( \mathrm{O}_{2} \) into two individual oxygen atoms.
• These free oxygen atoms can collide with other \( \mathrm{O}_{2} \) molecules to create ozone (\( \mathrm{O}_{3} \)).

Ozone is not just a static presence; it constantly regenerates through reactions with UV light and \( \mathrm{O}_{2} \), maintaining a balance in the stratosphere. This cycle is essential, as it ensures that a protective layer of ozone is constantly available to absorb harmful UV radiation.

Ultraviolet Radiation

Ultraviolet (UV) radiation is a type of energy produced by the Sun. It has shorter wavelengths than visible light, making it particularly high in energy. In the context of atmospheric science, UV radiation is most importantly divided into three categories:

• UV-A: With wavelengths from 320 to 400 nm, it has the lowest energy and is the least harmful.
• UV-B: Ranging from 280 to 320 nm, it can cause skin burns and other biological damage. The ozone layer absorbs most of this radiation.
• UV-C: With wavelengths from 100 to 280 nm, it is highly energetic and can be very destructive. Fortunately, it is completely absorbed by the \( \mathrm{O}_{2} \) and ozone in the stratosphere.

UV radiation is crucial in the formation of ozone in our atmosphere. It kick-starts the process by breaking apart \( \mathrm{O}_{2} \) molecules, leading to ozone formation. The stratosphere's ability to absorb various types of UV radiation is essential for protecting living organisms from its harmful effects, preventing severe health issues and environmental damage.