), which relate to how electrons and atoms oscillate when hit by an electric field. 1. Fundamental Interactions

The optical properties of solids describe how electromagnetic radiation—ranging from infrared to ultraviolet—interacts with condensed matter. This field is essential for developing technologies like lasers, solar cells, and fiber optics.

): Determines the speed of light in the material and how much it "bends" (refraction). Extinction Coefficient (

An increase in electrical conductivity caused by light absorption (used in light sensors).

): Represents how much light is lost to absorption as it travels through the solid. 4. Important Optical Phenomena

In the infrared range, light interacts directly with the vibrations of the crystal lattice (phonons). 5. Applications in Technology