Infrared spectroscopy is the study of the interaction between matter and electromagnetic radiation in the infrared region. This type of spectroscopy is used to study the vibrations of molecules; typically, the energy of molecular vibrations is the same as that of infrared light. Because of this, infrared spectroscopy can be used to determine molecular characteristics, such as bond length, bond angles, vibrational frequencies, and, indirectly, bond strengths. In addition, infrared spectroscopy is tremendously useful in determining the presence of certain characteristic groups in large molecules.

The electromagnetic spectrum consists of radiation having very high energy and frequency and short wavelength (such as gamma and x rays) to radiation having very low energy and frequency and long wavelength (such as radio waves). Visible light falls approximately in the middle of this spectrum. Infrared radiation has an energy that is lower than that of red light in the...