From The Collaborative International Dictionary of English v.0.44 [gcide]:
Photochemical \Pho'to*chem"ic*al\, adjective [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.
From WordNet (r) 2.0 [wn]:
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