Formation of ozone in the upper atmosphere from oxygen takes place by the action of

Options

A. cosmic rays
B. ultraviolet rays
C. free radicals
D. nitrogen oxides

Answer

To solve the question regarding the formation of ozone in the upper atmosphere from oxygen, we can break it down into a series of steps:

### Step-by-Step Solution:

1. **Understanding the Components**:
- We start with molecular oxygen (O₂) in the atmosphere.
- The process involves the conversion of O₂ into ozone (O₃).

2. **Role of Ultraviolet (UV) Rays**:
- The formation of ozone occurs in the upper atmosphere, specifically in the stratosphere, where ultraviolet (UV) radiation from the sun is present.
- UV rays have enough energy to break the bonds in O₂ molecules.

3. **Dissociation of Oxygen**:
- When UV rays strike O₂, they cause the molecule to dissociate into two free oxygen atoms (O).
- The reaction can be represented as:
\[ \text{O}_2 \xrightarrow{\text{UV}} 2 \text{O} \]

4. **Formation of Ozone**:
- The free oxygen atoms (O) produced can then react with other O₂ molecules in the presence of UV radiation to form ozone (O₃).
- This reaction can be represented as:
\[ \text{O} + \text{O}_2 \xrightarrow{\text{UV}} \text{O}_3 \]

5. **Conclusion**:
- Therefore, the formation of ozone in the upper atmosphere from oxygen occurs due to the action of ultraviolet rays.

6. **Identifying the Correct Option**:
- Based on the above explanation, we can conclude that the correct answer to the question is that ozone formation is facilitated by ultraviolet rays.

### Final Answer:
The formation of ozone in the upper atmosphere from oxygen takes place by the action of **ultraviolet rays**.