Actinism

Actinism is a property of radiation (particularly solar radiation) that leads to the production of photochemical effects. Actinism is derived from Greek with the meaning a radiant force. The word actinism seems to be used particularly in terms of imaging technology especially photography although it is used in medical literature for photo-biochemical effects such as a sunburn or radiation exposure from ultraviolet rays and in chemistry for containers that protect from photo-degradation. Chemical photography and X-ray imaging are two applications of actinism.

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In chemical terms actinism is the property of radiation that lets it be absorbed by a molecule and cause a photochemical reaction as a result. Einstein was the first to correctly theorize that each photon would be able to cause only one molecular reaction. This distinction separates photochemical reactions from exothermic reduction reactions triggered by radiation.

For general purposes photochemistry is the commonly used vernacular rather than actinic or actino-chemistry which are again more commonly seen used for photography or imaging. In medicine actinic effects are generally described in terms of the dermis or outer layers of the body such as eyes (see: Actinic conjunctivitis) and upper tissues that the sun would normally affect, rather than deeper tissues that shorter higher energy wavelength radiation such as x-ray and gamma might affect (see actinic keratosis).

Actinic chemicals include silver salts used in photography and other light sensitive chemicals.

Actinic inspection of masks in computer chip manufacture refers to inspecting the mask with the same wavelength of light that the lithography system will use.

Actinic lights are used in aquariums to encourage plant and coral growth. They give off a bluish tint.