optics
    n 1: the branch of physics that studies the physical properties
         of light
    2: optical properties; "the optics of a telescope"

Optics \Op"tics\, n. [Cf. F. optique, L. optice, Gr. ? (sc. ?).
   See Optic.]
   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.
   [1913 Webster]