Phosphorescence is the continued emission of light after exposure to UV or X-ray stimulation stops. Which option best expresses this?

• A. Emission of light due to heating.
• B. Immediate emission during exposure.
• C. Absorption of light without emission.
• D. Continued emission of visible light after stimulation stops.

Answer: (D)

The concept here is about light that keeps glowing after the stimulating energy is removed. Phosphorescence describes a material that stores energy from UV or X-ray exposure and then slowly releases it as light, so you can still see emission even after the stimulus stops. That lingering glow is what sets phosphorescence apart from fluorescence, where light is emitted only while the material is being stimulated and stops immediately when the energy source is removed. The other options describe different phenomena: light emitted because of heating is a different kind of luminescence, not phosphorescence; emission that happens during exposure is fluorescence; and absorption without emission isn’t luminescence at all. So the description of continued emission after stimulation stops best matches phosphorescence.