dI = −κ ρ I ds

∫ \frac{dI}{I} = −∫_{0}^{s} κρds
ln(I/I_{0}) = −κρ∫_{0}^{s} ds

= −κρs

\begin{aligned}\frac{I}{I_{0}} & = e^{−κρs} \\ & = e^{−s/ℓ} \end{aligned}

\begin{aligned}\frac{I}{I_{0}} & = e^{−κρs} \\ & = e^{−τ} \end{aligned}

I(X) = I_{0}e^{−cX} m(X) = m_{0} + kX

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