Spectrophotometry is a technique used to measure how much a chemical substance absorbs or transmits light at different wavelengths. This technique is commonly used in various fields such as chemistry, biochemistry, and environmental science to quantify the amount of a specific substance in a sample. Spectrophotometers are often used to analyze the concentration of a compound in a solution by measuring its absorption or transmission of light at specific wavelengths. This information can help researchers identify and quantify substances in a sample, determine reaction kinetics, and monitor changes in concentration over time. Overall, spectrophotometry is a versatile and widely used analytical tool in scientific research.