The extinction coefficient can be measured using techniques such as [UV-Vis spectroscopy](), where the absorbance of a material is plotted against wavelength. The value of ε can then be extracted using Beer-Lambert Law, which relates absorbance (A) to concentration (c), path length (l), and extinction coefficient (ε) as follows: A = εcl. For [nanoparticles](), additional considerations such as [scattering]() and [quantum confinement]() effects might need to be taken into account.
