Spectroscopy:

Spectroscopy is a method of analysis based on the interaction of electromagnetic radiation and matter. In other words, spectroscopy is the study of interaction of light with matter. Modern experimental chemistry uses many spectroscopic techniques viz. ultraviolet and visible spectroscopy, infrared spectroscopy, nuclear magnetic resonance spectroscopy, and electron spin resonance spectroscopy. All depend in some manner on the absorption of energy by a collection of molecules, the energy involved being in different regions of the electromagnetic spectrum.

The visible spectrum constitutes a small part of the total radiation spectrum. Most of the radiation that surrounds us cannot be seen, but can be detected by dedicated sensing instruments. This electromagnetic spectrum ranges from very short wavelengths (including gamma and x-rays) to very long wavelengths (including microwaves and broadcast radio waves). The following chart displays many of the important regions of this spectrum, and demonstrates the inverse relationship between wavelength and frequency.