Density of black body radiation

AI Thread Summary
The discussion centers on the formula for radiant energy density, expressed as 4 * sigma * T^4 / c, and its relationship to the Stefan-Boltzmann law. There is confusion regarding the use of 4 instead of 4*pi in the formula. Participants reference the Stefan-Boltzmann law, which states j = sigma * T^4 in watts/meter^2, to clarify the differences. The inquiry also raises questions about the inclusion of the speed of light, c, in the formula. Overall, the conversation seeks to reconcile these formulas and their implications in black body radiation.
asub
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I came across a formula that gives radiant energy density as 4 * sigma * T^4 / c. I am trying to figure out how this formula follows from Stefan-Boltzmann law. Shouldn't it be 4*pi instead of just 4? I am also wondering why one can just stick in c.

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