UV-visible spectroscopy is a technique that uses light in the UV and visible range to analyze compounds. It works by measuring how much light is absorbed by a sample at each wavelength. There are several types of electronic transitions that can occur, leading to absorption of light. The position and intensity of absorption bands provides information about features of molecules like conjugation and substituents. Beer's law states that absorbance is directly proportional to concentration and path length, allowing for quantitative analysis of samples.