noun
actinic rays; actinic light
Technical term in physics and chemistry for light that causes photochemical reactions, especially ultraviolet and shorter wavelengths.
化学線は写真フィルムを感光させる。
Actinic rays expose photographic film.
Compound of 化学 (かがく, 'chemistry') and 線 (せん, 'ray'). The term is a direct translation of the English 'actinic rays'.