Relating to chemical reactions or changes that are caused or influenced by radiation, particularly ultraviolet or X-ray light.
From actino- (from Greek aktis meaning 'ray') + chemical (from Medieval Latin alchemia). The prefix actino- became common in scientific terminology in the 19th century to describe ray-based or radiant phenomena.
Photography and early photochemistry relied heavily on actinochemical reactions—the reason old photographers had to work in dim 'red light' labs was because their film was extremely sensitive to blue and ultraviolet light, which carry the most actinochemical energy.
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