Stratosphere contains a stable layer of ozone molecules which absorbs UV radiation from the sun. The presence of ozone in atmosphere serves, as a shield to protect living organism on earth from the harmful effects of the solar ultraviolet radiation. The ultraviolet radiation are known to cause skin cancer. Ozone is formed in stratosphere by the following photochemical reactions.
`O_(2)(g)overset(UV)rarrO(g)+O(g)`
`O(g)+O_(2)(g)overset(UV)hArrO_(3)(g)`
Ozone is thormodhynamically unstable and ecomposes to molecular oxygen. Thus a dynamic equilibrium exits between the production and decomposition of ozone molecules.
Earth is protected from UV radiation by

Options

A. Carbon dioxide layer
B. Nitrogen layer
C. Ozone layer
D. Oxygen layer

Answer

To answer the question regarding how Earth is protected from UV radiation, we will break down the information provided and formulate a clear response.

### Step-by-Step Solution:

1. **Understanding the Role of Ozone**:
- The stratosphere contains a stable layer of ozone (O₃) that absorbs harmful ultraviolet (UV) radiation from the sun. This absorption is crucial as UV radiation can cause skin cancer and other harmful effects on living organisms.

2. **Formation of Ozone**:
- Ozone is formed through photochemical reactions in the stratosphere. The reactions are as follows:
- First, ultraviolet (UV) radiation splits molecular oxygen (O₂) into two monoatomic oxygen atoms (O):
\[ O_2(g) \overset{UV}{\rightarrow} O(g) + O(g) \]
- Then, one of these monoatomic oxygen atoms reacts with another O₂ molecule in the presence of UV light to form ozone (O₃):
\[ O(g) + O_2(g) \overset{UV}{\rightarrow} O_3(g) \]

3. **Dynamic Equilibrium**:
- Ozone is thermodynamically unstable and can decompose back into molecular oxygen:
\[ 2O_3(g) \rightleftharpoons 3O_2(g) \]
- This means there is a dynamic equilibrium between the production and decomposition of ozone in the stratosphere.

4. **Conclusion**:
- Given that ozone serves as a protective layer absorbing UV radiation, it is clear that the Earth is primarily protected from UV radiation by the **ozone layer**.

### Final Answer:
The Earth is protected from UV radiation by the **ozone layer**.

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