An invisible constituent of light which acts on a photographic plate and has other chemical effects; an actinic ray; an ultraviolet ray; usually in plural.
Origin
Early 19th century; earliest use found in Journal of Natural Philosophy, Chemistry and the Arts.
Definition of chemical ray in US English:
chemical ray
noun
historical
An invisible constituent of light which acts on a photographic plate and has other chemical effects; an actinic ray; an ultraviolet ray; usually in plural.
Origin
Early 19th century; earliest use found in Journal of Natural Philosophy, Chemistry and the Arts.