Which of the following is the coldest layer?

Options

A. Troposphere
B. Mesosphere
C. Stratosphere
D. thermosphere

Answer

To determine which layer of the Earth's atmosphere is the coldest, we can analyze the temperature characteristics of each layer. The layers of the atmosphere, in order from the surface of the Earth upwards, are:

1. **Troposphere**
2. **Stratosphere**
3. **Mesosphere**
4. **Thermosphere**

### Step-by-step Solution:

1. **Identify the Layers of the Atmosphere**:
- The atmosphere is divided into several layers: Troposphere, Stratosphere, Mesosphere, and Thermosphere.

2. **Understand Temperature Trends**:
- In the Troposphere, temperature decreases with altitude.
- In the Stratosphere, temperature increases with altitude due to the ozone layer absorbing UV radiation.
- In the Mesosphere, temperature again decreases with altitude.
- In the Thermosphere, temperature increases significantly due to solar activity.

3. **Examine the Temperature Ranges**:
- **Troposphere**: Generally, temperatures range from about 15°C at the surface to about -50°C at the top.
- **Stratosphere**: Temperatures can reach up to -3°C at the top, due to the presence of ozone.
- **Mesosphere**: This layer is known for its cold temperatures, ranging from about -27°C to -92°C.
- **Thermosphere**: Temperatures can rise to thousands of degrees Celsius, but this is due to the sparse air and not felt in the same way as at lower altitudes.

4. **Conclusion**:
- Based on the temperature ranges, the **Mesosphere** is identified as the coldest layer of the atmosphere, with temperatures dropping as low as -92°C.

5. **Final Answer**:
- Therefore, the correct answer to the question "Which of the following is the coldest layer?" is **Mesosphere**.