Which of the following law states that "good absorbers of heat are good emitters"

Options

A. Stefan's law
B. Kirchoff's law
C. Planks's law
D. Wien's law

Answer

To solve the question, we need to identify which law states that "good absorbers of heat are good emitters."

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a law that relates the ability of materials to absorb heat and emit heat.

2. **Identifying the Relevant Laws**:
- **Kirchhoff's Law**: This law states that at thermal equilibrium, the emissive power of a body is equal to its absorptive power. It implies that a good absorber of heat is also a good emitter of heat.
- **Stefan's Law**: This law relates to the total energy radiated per unit surface area of a black body per unit time, which is proportional to the fourth power of the black body's absolute temperature. It does not directly relate to absorptive and emissive properties.
- **Planck's Law**: This law describes the electromagnetic radiation emitted by a black body in thermal equilibrium at a definite temperature. It does not address the relationship between absorption and emission.
- **Wien's Law**: This law relates to the wavelength of the peak emission of a black body to its temperature. It does not address the relationship between absorption and emission.

3. **Conclusion**: Based on the definitions of the laws, Kirchhoff's Law is the one that states that good absorbers of heat are also good emitters of heat.

4. **Final Answer**: The correct option is Kirchhoff's Law.