Editing Absorbance (section)

=== Absorbance for scattering samples ===
For samples which scatter light, absorbance is defined as "the negative logarithm of one minus absorptance (absorption fraction: <math>\alpha</math>) as measured on a uniform sample".<ref name=":0" /> For decadic absorbance,<ref name=":1">{{cite book |doi=10.1002/0470027320.s8401 |chapter=Glossary of Terms used in Vibrational Spectroscopy |title=Handbook of Vibrational Spectroscopy |year=2006 |last1=Bertie |first1=John E. |isbn=0471988472 |editor1-first=Peter R |editor1-last=Griffiths }}</ref> this may be symbolized as {{nowrap|<math>\Alpha_{10}=-\log_{10}(1-\alpha)</math>.}} If a sample both transmits and [[Diffuse reflectance spectroscopy#Remission|remits light]], and is not luminescent, the fraction of light absorbed {{nowrap|(<math>\alpha</math>),}} remitted {{nowrap|(<math>R</math>),}} and transmitted {{nowrap|(<math>T</math>)}} add to 1: {{nowrap|<math>\alpha + R + T =1</math>.}} Note that {{nowrap|<math>1-\alpha = R+T </math>,}} and the formula may be written as {{nowrap|<math>\Alpha _{10}=-\log_{10}(R+T)</math>.}} For a sample which does not scatter, {{nowrap|<math>R=0 </math>,}} and {{nowrap|<math>1-\alpha = T</math>,}} yielding the formula for absorbance of a material discussed below.

Even though this absorbance function is very useful with scattering samples, the function does not have the same desirable characteristics as it does for non-scattering samples. There is, however, a property called [[Representative layer theory#Absorbing Power: The Scatter Corrected Absorbance of a sample|absorbing power]] which may be estimated for these samples. The [[Representative layer theory#Absorbing Power: The Scatter Corrected Absorbance of a sample|absorbing power]] of a single unit thickness of material making up a scattering sample is the same as the absorbance of the same thickness of the material in the absence of scatter.<ref>{{cite book |doi=10.1255/978-1-901019-05-6 |title=Interpreting Diffuse Reflectance and Transmittance: A Theoretical Introduction to Absorption Spectroscopy of Scattering Materials |year=2007 |last1=Dahm |first1=Donald |last2=Dahm |first2=Kevin |isbn=9781901019056 }}</ref>