Final answer:
Phosphorescence, known as afterglow, is a type of photoluminescence where materials emit light for an extended period after the excitation source is removed, due to slow decay of metastable states.
Step-by-step explanation:
Phosphorescence, also known as afterglow, is a type of photoluminescence related to fluorescence. Unlike fluorescence, which stops almost immediately when the excitation source is removed, phosphorescence continues to emit light for a longer duration due to atoms or molecules being excited to metastable states that decay slowly. Phosphorescent materials can absorb energy such as visible or ultraviolet light, store that energy, and then release it slowly over time as visible light.
An example of this process could include certain ceramics that, when cooled after firing, trap the excitation energy and later release it when heated. This process is known as thermoluminescence and can be used to date antiquities due to the gradual decrease in light emission over time, providing clues to the age of the ceramic piece.