What is the meaning of Actinic?

Related to radiation; used most often in reference to light, especially in the ultraviolet range.

Harsh and bright.

Caused by extensive exposure to ultraviolet light.

(chemistry, photography) Of or relating to actinism, the range of photochemical effects produced by exposure to EM radiation, particularly sunlight.

Composed of actin.

actinic

Source: wiktionary.org