The spectral radiance of a black body per unit solid angle is given by:
I ( λ , T ) = 2 h c 2 λ 5 1 e h c / λ k T − 1 {\displaystyle I(\lambda ,T)={\frac {2hc^{2}}{\lambda ^{5}}}\,{\frac {1}{e^{hc/\lambda kT}-1}}}
It can also be given as a function of frequency:
I ( ν , T ) = 2 h ν 3 c 2 1 e h c / λ k T − 1 {\displaystyle I(\nu ,T)={\frac {2h\nu ^{3}}{c^{2}}}\,{\frac {1}{e^{hc/\lambda kT}-1}}}
