Infrared (IR) spectrometers measure the wavelength and intensity of the absorption of infrared light by a sample. Infrared light lies between the visible and microwave portions of the electromagnetic spectrum and has a range of wavelengths. Near infrared light is closest in wavelength to visible light. By contrast, far infrared light is closest to the microwave region. Mid-infrared light is energetic enough to excite molecular vibrations to higher energy levels. These vibrations, which are caused by changes to a molecule’s dipole moment, occur only at those frequencies where the molecule absorbs infrared light. Because the wavelengths of infrared absorption bands are characteristic of specific types of chemical bonds, infrared spectrometers are often used to identify organic and organometallic molecules.