A spectrograph is an instrument used to separate light into its component colors, creating a spectrum. This allows scientists to analyze the light emitted or absorbed by objects, such as stars or gases. By examining the spectrum, researchers can determine the chemical composition, temperature, density, and motion of these objects. Spectrographs are commonly used in fields like astronomy and chemistry. In astronomy, they help identify the elements present in distant stars and galaxies, while in chemistry, they can analyze substances to understand their properties. Overall, spectrographs are essential tools for studying light and matter.