Differing formulae for power emission

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SUMMARY

The discussion centers on the differing formulas for Planck's Law of Radiated Power Density, specifically the presence of the constant π in the equations. The formula from HyperPhysics includes π, while the Wikipedia entry omits it. The HyperPhysics formula is expressed as Bf(T)=((2*pi*h*c^2)/(lambda^5))(1/(e^(h*c/lambda*k*T)-1)), while the Wikipedia version presents it without π. Additionally, the units differ, with HyperPhysics using watts per cubic metre and Wikipedia using watts per square metre per unit solid angle.

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PatF
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pi? i ate it!

PatF said:
What happened to pi?

Hi PatF! :smile:

(have a pi: π :smile:)

In wikipedia, the units are "spectral radiance", which involves watts per square metre per unit solid angle

but in hyperphysics it's watts per cubic metre. :wink:
 

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