The interaction of electromagnetic radiation with solids, liquids or gases produces various effects, such as absorbance, reflectance or scattering. UV VIS spectroscopy exclusively investigates the interaction of radiation with matter in the ultraviolet and visible range.

When atoms or molecules absorb electromagnetic radiation they are transformed from a ground state into an energetically excited state. Energy of a specific wavelength is absorbed in this process. The various molecular states have a relatively broad energy range in comparison with atoms. Rotation and vibration of a molecule can be stimulated in the infrared range. The absorbance of defined packets of energy (quanta) by the valence electrons is observed in the range of visible and ultraviolet light.