The outcome of an infrared analysis is a spectrum showing different peaks, with values of wavelength on the X-axis and intensity on the Y-axis. The main information from an IR spectrum comes from the consideration that many functional groups absorb at the same wavelength, regardless of the structure of the molecule. These peaks are called group frequencies and their position is influenced by the size of the atoms involved, the length of the bond, the electronegativity and the variation of dipole moment. For example, the hydroxyl group has a high difference in electronegativity between oxygen and hydrogen and shows its peak at high value of wavelength with a characteristic broad signal. The intensity of the peaks is mainly influenced by the concentration of the sample, but also by the dipole moment and other minor factors. The region between 400 cm-1 and 1500 cm-1 is called the fingerprint region, where many fine peaks can be found and it mainly contains bending vibrations. This region is usually not considered, as many functional groups absorb at higher values of wavelength, but it can be used for a fine overlap of peaks when identifying a precise compound.