Note: The concentration of the absorbing species can be quantified using the Beer–Lambert law (or Beer–Lambert–Bouguer law) \[A = \varepsilon cl = \lg\left(\frac{P_{0}}{P}\right)\] where \(\varepsilon\) is the molar absorption coefficient of the absorbing species, \(l\) is the absorption path length, and \(c\) the amount concentration. A sample is irradiated with a specific wavelength of light, typically in the ultraviolet or visible spectral region; the spectral radiant power of incident light on the sample (\(P_{0}\)) and transmitted radiation after passing through the sample (\(P\)) are used to calculate absorbance (\(A\)).