Here are 2 pieces of paper napkin that fell on snow while I was cross-country skiing on the golf course. The paper napkin is exhibiting fluorescence by Sun's ultraviolet (UV) light.
Photoluminescence (PL) is the general process where a substance absorbs light (photons) and re-emits light. Fluorescence and Phosphorescence are specific types of Photoluminescence (PL). UV fluorescence is when a material absorbs invisible ultraviolet (UV) light and re-emits it as visible light.
