A spectrophotometer is an analytical instrument used to measure the intensity of light at different wavelengths. It works by passing light through a sample and detecting how much light is absorbed or transmitted. This information helps determine the concentration of substances in a solution, making it valuable in fields like chemistry, biology, and environmental science. The device typically consists of a light source, a monochromator to select specific wavelengths, a sample holder, and a detector. By analyzing the light absorption patterns, researchers can identify and quantify various compounds, such as proteins, nucleic acids, and pollutants.