Apparent violation of kirchoff's law of thermal radiation

Kirchhoff's law states that the ratio of emissive power to absorptive power is constant, so e1/a1 = e2/a2 = const. However, the equation e1 = a1e2 is in violation of this law, as it implies that the emissive power is equal to the absorptive power. This may be where you have gone wrong. In summary, the conversation discusses the relationship between emissive power, absorptive power, and thermal equilibrium for two bodies A and B. The statement e1 = a1e2 is found to be in violation of Kirchhoff's law, which states that the ratio of emissive power to absorptive power should be constant for bodies in thermal equilibrium.
  • #1
Sunny Singh
18
1
suppose there are two bodies A and B with emissive powers e1 and e2 respectively and with absorptive powers a1 and a2 respectively... now both bodies are at the same temperature T. Hence e1/a1 = e2/a2 = const by kirchhoffs law.
for the body A, energy emitted is e1 and energy gained is a1e2. now as both of them are in thermal equilibrium at T,energy emitted minus gained must be zero. But then e1=a1e2 is in violation with the above equation of kirchhoffs law. Where have i gone wrong?
 
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  • #2
The absorbance and emissivity of a body in thermal equilibrium must be the same. So if understand your notation you have that a1=e1 and a2=e2.
 

1. What is Kirchoff's law of thermal radiation?

Kirchoff's law of thermal radiation states that for a given material, the ratio of its emissive power to its absorptive power is constant at a given temperature and wavelength. This means that a good absorber of radiation is also a good emitter of radiation at the same wavelength and temperature.

2. What is an apparent violation of Kirchoff's law of thermal radiation?

An apparent violation of Kirchoff's law of thermal radiation occurs when the ratio of emissive power to absorptive power is not constant for a given material at a given temperature and wavelength. This can happen due to various factors such as surface roughness, non-uniform temperature distribution, or spectral selectivity of the material.

3. Can Kirchoff's law of thermal radiation be violated?

No, Kirchoff's law of thermal radiation is a fundamental law of thermodynamics and has been experimentally verified. However, in certain situations, it may appear to be violated due to the factors mentioned above.

4. How do scientists explain apparent violations of Kirchoff's law?

Scientists have developed more comprehensive models, such as the Kirchoff-Planck law, to explain the behavior of materials that seem to violate Kirchoff's law. These models take into account factors such as surface roughness and spectral selectivity to provide a more accurate representation of the material's behavior.

5. What are the implications of apparent violations of Kirchoff's law of thermal radiation?

Apparent violations of Kirchoff's law do not have any significant implications on the validity of the law. However, they do highlight the importance of considering all factors that can affect the radiative properties of a material, especially in engineering and design applications.

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