What does the term "optical" relate to?

The term "optical" specifically pertains to how light interacts with materials. This includes various phenomena such as reflection, refraction, absorption, and transmission of light as it passes through or interacts with different substances. Understanding these interactions is crucial in fields such as optics, photonics, and nanotechnology, where controlling light at the nanoscale can lead to innovative applications like advanced imaging systems, sensors, and energy-efficient lighting. The focus is on the behavior of light rather than sound, chemical reactions, or electrical properties, which relate to different scientific principles and disciplines.