Earth is protected from UV rays by

Options

A. `N_(2)`
B. `O_(2)`
C. `O_(3)`
D. `SO_(3)`

Answer

To answer the question "Earth is protected from UV rays by", we need to analyze the options provided: N2, O2, O3, and SO3.

### Step-by-Step Solution:

1. **Understanding UV Protection**:
- The Earth is exposed to ultraviolet (UV) rays from the sun, which can be harmful to living organisms.

2. **Identifying the Protective Layer**:
- The protective layer against UV rays is primarily composed of ozone (O3), which is found in the stratosphere.

3. **Role of Ozone**:
- Ozone absorbs a significant portion of the harmful UV radiation, filtering it before it reaches the Earth's surface. This is crucial for protecting humans and other living organisms.

4. **Formation of Ozone**:
- Ozone is formed in the atmosphere when oxygen molecules (O2) are exposed to UV light. The UV radiation splits O2 molecules into individual oxygen atoms (O). These single oxygen atoms can then react with other O2 molecules to form ozone (O3).

5. **Evaluating the Options**:
- **N2 (Nitrogen)**: While nitrogen is abundant in the atmosphere, it does not play a role in UV protection.
- **O2 (Oxygen)**: Oxygen is essential for the formation of ozone but does not directly protect against UV rays.
- **O3 (Ozone)**: This is the correct answer, as ozone is specifically known for its ability to absorb UV radiation.
- **SO3 (Sulfur trioxide)**: This compound does not have a role in UV protection.

6. **Conclusion**:
- Based on the analysis, the correct answer is **O3 (Ozone)**, as it is the gas that protects the Earth from harmful UV rays.

### Final Answer:
Earth is protected from UV rays by **O3 (Ozone)**.