Students of chemistry, Chemical Engineering, Physics, biochemistry, geology, medical sciences, engineering and environmental sciences must develop an understanding of these tools and techniques so that they may be able to solve the analytical problems.The Author believes that the correct choice and efficient use of modern analytical requires an understanding of the fundamental principles of operation of these measuring instruments and devices. After attaining such understanding, the student pre- analyst can reasonably make choices among the various alternative means of solving an analytical problem. With this aim in mind, it is the objective of the author to give the student an introduction to the principles of spectroscopy.The scope of this book is to give the scholars plenty of focused ideas in the basic theory which makes understandable the relationship of the amount of electromagnetic radiation absorbed or emitted by a sample and the properties of atoms or molecules of the sample.