Actinisch

Actinisch is a Dutch term meaning actinic in English. It is used to describe radiation that can cause photochemical reactions, as opposed to purely thermal effects. In practice, actinic radiation refers primarily to ultraviolet light, and in some contexts to the portion of visible light with sufficient energy to initiate chemical changes. Wavelengths typically associated with actinic effects lie roughly below 420 nanometers, though definitions vary by field.

In photography and printing, actinic light denotes the part of the spectrum capable of exposing photographic emulsions. Early photography distinguished actinic from non-actinic radiation. Modern photographic films and digital sensors are designed to be sensitive to UV and violet-blue light, while protective filters may block these wavelengths to prevent unwanted exposure.

Actinic exposure can damage biological tissues and materials. In dermatology, chronic actinic exposure from sunlight contributes to photoaging and increases the risk of actinic keratosis and skin cancer. In ophthalmology, actinic radiation can harm the cornea and lens, contributing to cataracts. In materials science, actinic photons can degrade polymers and dyes, altering color and strength over time.

Measurement of actinic irradiance is performed with actinometers or UV radiometers. Protective strategies include using sunscreen and clothing with UV protection, sunglasses that block UV and violet-blue light, and optical filters that absorb actinic wavelengths in various settings such as laboratories, photochemical work, and medical facilities.