1859, "of or pertaining to the chemical action of light," from photo- + chemical. Related: Photochemically.
Entries linking to photochemical
photo-
word-forming element meaning "light" or "photographic" or "photoelectric," from Greek photo-, combining form of phōs (genitive phōtos) "light" (from PIE root *bha- (1) "to shine").
chemical adj.
1570s, "relating to chemistry, pertaining to the phenomena with which chemistry deals," from chemic "of alchemy" (a worn-down derivative of Medieval Latin alchimicus; see alchemy) + -al (1). In early use also of alchemy. Related: Chemically. Chemical warfare is attested from 1917.