This deals with the infrared region of the electromagnetic spectrum. It uses the fact that molecules absorb certain resonant frequencies that are characteristic of their structure and chemical nature. As such, as a beam of infrared light passes through a sample absorption occurs, where the frequency of light matches the vibrational frequency of a bond. Examination of the transmitted light reveals how much energy was absorbed at each wavelength and a transmittance or absorbance spectrum can be produced. Analysis of these characteristics reveals details of the molecular structure of a sample.