Apparent violation of kirchoff's law of thermal radiation

AI Thread Summary
In the discussion, the relationship between emissive and absorptive powers of two bodies in thermal equilibrium is analyzed using Kirchhoff's law. It is established that for bodies A and B at the same temperature T, the ratio of emissive to absorptive powers must be constant. The confusion arises when attempting to equate the energy emitted by body A with the energy absorbed from body B, leading to the equation e1 = a1e2. The error is identified in the assumption that emissivity and absorptivity are equal when they are not necessarily the same in all contexts. The conclusion emphasizes the need for clarity in the definitions of emissive and absorptive powers to resolve the apparent contradiction.
Sunny Singh
Messages
19
Reaction score
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?
 
Science news on Phys.org
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.
 

Thread 'Condensate rate of water for an air conditioning cooling coil'

I need to calculate the amount of water condensed from a DX cooling coil per hour given the size of the expansion coil (the total condensing surface area), the incoming air temperature, the amount of air flow from the fan, the BTU capacity of the compressor and the incoming air humidity. There are lots of condenser calculators around but they all need the air flow and incoming and outgoing humidity and then give a total volume of condensed water but I need more than that. The size of the...
View full post »
Thread 'Why work is PdV and not (P+dP)dV in an isothermal process?'

Thread 'Why work is PdV and not (P+dP)dV in an isothermal process?'

Let's say we have a cylinder of volume V1 with a frictionless movable piston and some gas trapped inside with pressure P1 and temperature T1. On top of the piston lay some small pebbles that add weight and essentially create the pressure P1. Also the system is inside a reservoir of water that keeps its temperature constant at T1. The system is in equilibrium at V1, P1, T1. Now let's say i put another very small pebble on top of the piston (0,00001kg) and after some seconds the system...
View full post »

Similar threads

Clarification about Kirchhoff's law of thermal radiation
Replies
6
Views
2K
Questions About Stephan's Law of Thermal Radiation
Replies
5
Views
2K
Question about thermal radiation
Replies
2
Views
1K
A Average temperature in a greenhouse
Replies
2
Views
2K
Thermal radiation, emissivity and Kirchhoff
Replies
4
Views
2K
Contradiction with Kirchhoff's Radiation Law?
Replies
4
Views
2K
The Second Law of Thermodynamics and the Stefan-Boltzmann Law
Replies
6
Views
2K
How to calculate thermal radiation intensity without surfaces?
Replies
10
Views
2K
How is the 2nd law of thermodynamics obeyed in this system?
Replies
1
Views
6K
Black body radiation, Planck's law, derivation
Replies
2
Views
8K

Hot Threads

Recent Insights

Back
Top