ABSTRACT
The emission of light is one of the most fascinating phenomena in nature. Everybody feels the beauty while looking at the colors when the sun is going down, when a thunder illuminates the night, or when the emission of the aurora moves like magic in the dark heaven. And every day we are looking at something in order to read information from a computer screen, to drive not into but around an obstacle, and to look into the eyes of the child to understand that it tries to hide that it just burned off father’s stamp collection in an unlucky physical experiment. In general terms, we all use light to obtain information, to diagnose something, to control or optimize a process, or to understand what is true and what is right. The basic science related to all these questions is called “spectroscopy,” and questions such as “Why the heaven is blue?”, “What is the temperature in the flame of a candle?”, “What makes the sun burning so wonderful?” have been the historical origin of scientific activity. We also might ask what light is by itself? This is a difficult question: although we have some imagination what light is, it is difficult to say what it really is and the interesting reader is referred to an excellent textbook devoted to this question [1].
