Light and Optics — Definition

Definition

Optics is the study of light, its interaction with matter and the formation of images. Geometrical optics represents propagation by rays when the relevant dimensions are large compared with wavelength.

Reflection redirects light at a surface; refraction concerns propagation across media with different refractive indices. Mirrors and lenses form images through these mechanisms. A real image involves actual ray convergence, while a virtual image is located by extending rays backward.

Frequency, wavelength and speed are distinct quantities. The ray model explains many instruments, but diffraction and energy exchange require additional wave or quantum descriptions when their effects become important.