5. Glossary

Extinction coefficient; extinction coefficient

Also known as the attenuation coefficient of a substance, it measures the energy loss of electromagnetic radiation passing through the medium. Similar to the absorption coefficient, it also takes into account the effects of scattering and luminescence, in addition to absorbance. It depends on material and wavelength. It is the imaginary part of the complex refractive index. Transparent materials (glasses, for example) have a low extinction coefficient, while opaque materials have a high extinction coefficient.