1. the property of radiation (especially ultraviolet light) that produces chemical changes, such as in photography or on living organisms
Usage: technical; chiefly used in physics and chemistry

Examples

• The actinism of ultraviolet light is strong enough to cause sunburn on exposed skin.
• Photographers must account for actinism when working with certain film types.
• The actinism of the sun's rays affects the rate of photosynthesis in plants.
• Early chemists studied actinism to understand how light could trigger chemical reactions.
• The actinism of short-wavelength radiation makes it useful for sterilization purposes.