Ultraviolet and visible (UV-Vis) absorption spectroscopy is the measurement of the attenuation of a beam of light after it passes through a sample or after reflection from a sample surface. The absorbance of a solution increases as attenuation of the beam increases. The concentration of an analyte in solution can be determined by measuring the absorbance at a specific wavelength. UV-Vis spectroscopy is usually applied to molecules or inorganic complexes in solution.