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roam
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Homework Statement
The following is from a book:
"Terrestrial radiation, T=255 K. Emitted flux ≈ 240 W m-2. Energy density for cavity radiation ≈ 3x10-6 J m-3. Entropy for cavity radiation ≈ 1.7x10-8 J K-1 m-3."
I can't understand how they have calculated the Entropy.
The Attempt at a Solution
So, I can't understand when calculating the entropy using [itex]S=\frac{4}{3} aT^3V[/itex], what value they were using for "V"? V has to be the volume of the blackbody and we are treating Earth as one. So I used the volume of Earth, however my calculations do not match the book.
From Kirchhoff’s Law aλ = ελ. And
[itex]Flux \ = \ \frac{ac}{4} T^4 = \sigma T^4 \implies a = 7.56 \times 10^{-16}[/itex]
[itex]S= (4/3)(7.56 \times 10^{-16})(255)^3(1.083206 \times 10^{21}) = 1.8105 \times 10^{13}[/itex]
The results are very different. I was wondering if I'm missing something here or the book is wrong?
Any help is appreciated.
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