Optics, the study of light, is a diverse field of science concerned with how light is produced and transmitted and how it interacts with matter.
Light sometimes behaves like a particle and sometimes like a wave.
When it is emitted or absorbed by atoms, light behaves as though it were composed of particles, or packets of energy called photons. The branch of geometrical optics is concerned with the principles that govern the image-forming properties of mirrors, lenses, and similar devices. It deals, in part, with what happens when light strikes different types of surfaces. A light ray passing through a vacuum or a transparent substance moves in a straight path. When it strikes the surface of a different substance, part of it bounces off, or is reflected.