Absorption spectra refer to the specific wavelengths of light that are absorbed by a substance, typically a gas or liquid. When light passes through a material, certain wavelengths are absorbed by the atoms or molecules, resulting in a spectrum that shows dark lines or bands at those wavelengths. This occurs because the energy of the absorbed light matches the energy required to excite electrons in the atoms. These spectra are unique to each element or compound, much like a fingerprint. Scientists use absorption spectra to identify substances and analyze their composition in various fields, including astronomy, chemistry, and environmental science.