The Difference Between Fluorescence & Phosphorescence:
What is Fluorescence?
Some materials absorb invisible, high-energy "black" (ultraviolet) light, use part of the energy, then emit nanoseconds later bright visible light, but only while the ultraviolet light shines on it.
What is Phosphorescence?
Phosphorescence is similar to fluorescence. Both involve absorption of energy. "Glow-in-the-dark" light (phosphorescence) is not as bright as fluorescence but lasts much longer. Phosphorescence is controlled by "forbidden" quantum physics transitions.
Quantum Physics Transitions
Quantum physics transitions are changes in molecular states made possible by energy absorption. Energy changes are quantized if they can only be absorbed or emitted in predetermined values or "quanta." After absorption, lower energy photons (light particles) can be re-emitted.
Fluorescence is utilized in medicine, while phosphorescence is used for glow-in-the-dark products.
Mineralogists treasure fluorescent rocks.