To radiant energy, such as x-rays, ultraviolet light, and sunlight, especially the photochemical effects.
Actinic, pertaining to alterations induced by ultraviolet rays from sunlight, encompasses conditions such as actinic dermatitis (inflammation of the skin) and actinic keratosis (roughness and thickening of the skin). These conditions arise as a consequence of excessive exposure to solar radiation.
Referring to light rays located past the violet segment of the spectrum, which induce chemical reactions.