${\displaystyle L={\frac {1}{\cos \theta )){\frac {dI}{dS))}$

${\displaystyle \cos \theta ={\boldsymbol {n))\cdot {\boldsymbol {k))}$

${\displaystyle L=\int _{0}^{\infty }K(\lambda )\,L_((\text{e)),\lambda }\,d\lambda =K_{\text{m))\int _{0}^{\infty }V(\lambda )\,L_((\text{e)),\lambda }\,d\lambda }$

${\displaystyle M={\frac {d\varPhi _{\text{src))}{dS))={\frac {d}{dS))\int _{\text{ext))I\,d\omega =\int _{\text{ext))L\cos \theta \,d\omega }$

${\displaystyle M=\oint d\phi \int _{0}^{\pi /2}L(\theta ,\phi )\cos \theta \sin \theta \,d\theta }$

${\displaystyle M=\pi L}$