Source : Webster's Revised Unabridged Dictionary (1913)

Photochemical \Pho`to*chem"ic*al\, a. [Photo- + chemical.]
   (Chem.)
   Of or pertaining to chemical action of light, or produced by
   it; as, the photochemical changes of the visual purple of the
   retina.

Source : WordNet®

photochemical
     adj : of or relating to or produced by the effects of light on
           chemical systems