Choose the correct statements from the following `:`

Options

A. Good reflector are good emitters of thermal radiation.
B. Burns caused by water at `100^(@)C` are more severe than those caused by steam at `100^(@)C`.
C. If the Earth did not have atmosphere, it would become intolerably cold.
D. It is impossible to construct a heat engine of a `100%` efficiency.

Answer

To solve the question of choosing the correct statements, we will analyze each statement provided and determine its validity based on principles of physics, particularly thermodynamics and heat transfer.

### Step-by-Step Solution:

1. **Statement 1: Good reflectors are good emitters of thermal radiation.**
- **Analysis:** This statement is incorrect. According to Kirchhoff's law of thermal radiation, good absorbers of thermal radiation are also good emitters. Good reflectors tend to reflect thermal radiation rather than absorb it, which means they are not effective emitters.
- **Conclusion:** This statement is **false**.

2. **Statement 2: Burns caused by water at 100 degrees Celsius are more severe than those caused by steam at 100 degrees Celsius.**
- **Analysis:** This statement is also incorrect. While both water and steam are at the same temperature, steam contains more thermal energy due to its latent heat. When steam condenses, it releases this latent heat, causing more severe burns compared to water at the same temperature.
- **Conclusion:** This statement is **false**.

3. **Statement 3: If the Earth did not have an atmosphere, it would have become intolerably cold.**
- **Analysis:** This statement is correct. The Earth's atmosphere contains greenhouse gases that trap heat from the sun. Without this atmosphere, heat would escape back into space, leading to extremely low temperatures at night, similar to those observed on other planets without atmospheres.
- **Conclusion:** This statement is **true**.

4. **Statement 4: It is impossible to construct a heat engine of 100% efficiency.**
- **Analysis:** This statement is correct. According to the second law of thermodynamics, no heat engine can be 100% efficient because some energy is always lost as waste heat. Thus, it is impossible to convert all input energy into work without some loss.
- **Conclusion:** This statement is **true**.

### Final Summary of Statements:
- Statement 1: **False**
- Statement 2: **False**
- Statement 3: **True**
- Statement 4: **True**

### Correct Statements:
The correct statements from the options provided are:
- Statement 3: If the Earth did not have an atmosphere, it would have become intolerably cold.
- Statement 4: It is impossible to construct a heat engine of 100% efficiency.

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