Applied spectroscopy is the application of various spectroscopic methods for detection and identification of different elements/compounds in solving problems in the fields of forensics, medicine, oil industry, atmospheric chemistry, pharmacology, etc. A common spectroscopic method for analysis is Fourier transform infrared spectroscopy, where chemical bonds can be detected through their characteristic infrared absorption frequencies or wavelengths. These absorption characteristics make infrared analyzers an invaluable tool in geoscience, environmental science, and atmospheric science. For instance, atmospheric gas monitoring has been facilitated by the development of commercially available gas analyzers which can distinguish between carbon dioxide, methane, carbon monoxide, oxygen, and nitric oxide. The text will benefit post graduate students at M.Sc., M.Phil. and research in chemistry, physics, biology and pharmacology.