Introduction:

• Materials are important in everyday life, as they do play an important role because of their fundamental physical properties such as electrical, thermal, magnetic and optical. We have already discussed the ways to characterize the thermal, electrical and magnetic properties.

• Optics being one of the branches of physics deals with the behavior and properties of light including its interaction with matter. Therefore, the optical property of the materials is one of the most important properties, which helps to understand the interaction of light with the materials and provides important information on structural properties. The optical properties of the materials are useful in different applications.

• When the light interacts with the materials, various phenomena, such as absorption (materials absorb the incoming photon energy), reflection (photons of identical energy are immediately emitted by the materials), transmission (photons may not interact with the structure), and refraction (transmission photons change the velocity) occur due to the change in the electronic or crystal structure of the materials.

• Spectroscopy is the technique to study the interaction of light (electromagnetic radiation) with the matter to obtain the physical and chemical nature of the materials. The basics of spectroscopy can be studied from already available lectures in NPTEL portal: http://nptel.ac.in/courses/102103044/3