D defs.my
Entry 1 sense Webster, 1913

Optics

/äp'-tĭks/ · Op·tics · IPA /ˈɑptɪks/
01 n. That branch of physical science which treats of the nature and properties of light, the laws of its modification by opaque and transparent …
  1. 1.
    That branch of physical science which treats of the nature and properties of light, the laws of its modification by opaque and transparent bodies, and the phenomena of vision.