A Fabry-Perot Interferometer allows the incident radiation to be reflected back and forth between a pair of reflective plates that are separated by an air gap (Ingle). An optical spectrometer, like the Ossila USB spectrometer, is the most common type. Spectroscopy is the study of the interaction of. In this Chapter, we will introduce a general notion of spectroscopy as a method and of its most basic type of data, a spectrum. We will also introduce the most basic features of each spectroscopic signal (spectral line or resonance): position, intensity and width/lineshape. From this information, we can often deduce a great deal of additional insight, including: Molecular identities –. % absorptance. However, the curve e slop r experimen rba les per litre. The units for molar absorptivity are lit eed 1. They may exhibit va nt m on take place.