Spectroscopy is the study of the interaction between matter and electromagnetic radiation. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, by a prism. Later the concept was expanded greatly to include any interaction with radiative energy as a function of its wavelength or frequency, predominantly in the electromagnetic spectrum, though matter waves and acoustic waves can also be considered forms of radiative energy; recently, with tremendous difficulty, even gravitational waves have been associated with a spectral signature in the context of LIGO and laser interferometry. Spectroscopic data are often represented by an emission spectrum, a plot of the response of interest as a function of wavelength or frequency.

In the present book, fifteen typical literatures about spectroscopy published on international authoritative journals were selected to introduce the worldwide newest progress, which contains reviews or original researches on electromagnetic spectrum, acoustic wave, emission spectrum, biomedical spectroscopy, wavelength, etc. We hope this book can demonstrate advances in spectroscopy as well as give references to the researchers, students and other related people.