Derivation of Stefan-Boltzmann Law from Wien's Law

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Homework Help Overview

The discussion centers around deriving the Stefan-Boltzmann Law from Wien's Law, specifically exploring the relationship between these two laws in the context of black body radiation. Participants are examining the implications of the provided hints and equations related to the laws.

Discussion Character

  • Conceptual clarification, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Some participants attempt to manipulate Wien's Law algebraically to derive the Stefan-Boltzmann Law, expressing uncertainty about the effectiveness of this approach.
  • Others question whether the problem is correctly framed, suggesting that deriving the Stefan-Boltzmann Law may require integrating over the Planck distribution rather than relying solely on Wien's displacement law.
  • There is a suggestion that the original poster might need to consider Wien's distribution law instead of the displacement law for a more comprehensive approach.
  • Participants express confusion regarding the physical meaning of the hints provided in the problem statement.

Discussion Status

The discussion is ongoing, with various interpretations being explored. Some participants have offered insights into the necessity of integrating over distributions to derive the Stefan-Boltzmann Law, while others are still grappling with the initial steps of the derivation. There is no explicit consensus on the approach to take, but the dialogue is fostering a deeper examination of the concepts involved.

Contextual Notes

Participants note potential constraints in the problem setup, including the ambiguity of the hints and the specific forms of Wien's Law that should be applied. There is also a mention of differing interpretations of Wien's Law, which may affect the derivation process.

PhysicsItHertz
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Homework Statement



Derive Stefan-Boltzmann Law from Wien's Law.
Hint: You can use (without proof) R(T)=∫(-∞ to ∞) R(λ,T)dλ, p(λ,T)= 4/c R(λ,T).



Homework Equations


Stefan-Boltzmann Law:P=AσT^4
Wien's Law: λmax=(2.898*10^-3 m*K)/T.

The Attempt at a Solution


Let λmax=(2.898*10^-3 m*K)/T.

Using cross multiplication gives: T=(2.898*10^-3m*K)/λmax.

Raising both sides to the fourth power gives: T^4=(2.898*10^-3m*K)^4/(λmax)^4.

Multiplying both sides by λmax^4 gives: T^4*(λmax)^4=(2.898*10^-3m*K)^4.

Im not really sure if this going to go anywhere.
My idea was to just algebraically manipulate Wien's Law to equate to Stefan-Boltzmann Law.

The issue I have with doing this is that I am not sure what the hint even means (physically).
 
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I don't think you can actually derive the Stefan-Boltzmann law from Wien's displacement law... the SB law requires an integral over all wavelengths of the Planck distribution basically. Wien's displacement law just tells you where the maximum of the Planck distribution is, and that is not enough information to do the problem. Are you sure the problem is asking you to derive SB from Wien's displacement law? o.o
 
PhysicsItHertz said:
Derive Stefan-Boltzmann Law from Wien's Law.
Hint: You can use (without proof) R(T)=∫(-∞ to ∞) R(λ,T)dλ, p(λ,T)= 4/c R(λ,T).

Could it be that you are meant to base the derivation on Wien's distribution law rather than Wien's displacement law? Your hint seems to indicate that you are to integrate over some distribution law.

You should be able to use Wien's distribution law to show that the total power radiated is proportional to T4. However, I don't think you will get the correct numerical value for the proportionality constant.
 
I am currently working on the same question except for wien's law we are supposed to use wien's law: p(λ,T) = f(λ,T)/^5 (maybe op and I are in the same class lol). I also could use some help with this problem. Honestly I have no idea where to even begin.
 
Tirain said:
I am currently working on the same question except for wien's law we are supposed to use wien's law: p(λ,T) = f(λ,T)/^5 (maybe op and I are in the same class lol). I also could use some help with this problem. Honestly I have no idea where to even begin.

Did you mean to write p(λ,T) = f(λT)/λ5, where f is some undetermined function of the product of λ and T? That's the most general form of Wien's displacement law. I suspect that the OP was also supposed to use this form of Wien's law. The Wien's distribution law that I linked to in a previous post is a special case this general law. But the one I linked to is only an approximate formula that is accurate in the range of short wavelengths. I had forgotten about the general law that you are using.

Anyway, you should be able to derive the Stefan-Boltzmann law from p(λ,T) = f(λT)/λ5. Think about the meaning of p(λ,T) and how you would use p(λ,T) to find the total power radiated for all wavelengths.
 

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