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What is fluorescence?
Quick answer
Fluorescence is when a material absorbs light at one color and quickly re-emits it at another, usually glowing under ultraviolet light. The material soaks up high-energy light and releases it as visible light — the effect behind highlighter pens and blacklight posters.
Key things to understand
- A substance absorbs light (often invisible UV) and re-emits visible light.
- The emitted light is lower energy, a different color than absorbed.
- It stops the instant the light source is removed.
- It's behind highlighters, blacklight effects, and some minerals' glow.
- Phosphorescence is similar but keeps glowing after the light stops.
People also ask
What causes fluorescence?
A material absorbs high-energy light, its electrons jump up, then drop back down releasing the energy as visible light of a different color.
What's the difference between fluorescence and phosphorescence?
Fluorescence stops instantly when the light is removed; phosphorescence stores the energy and keeps glowing for seconds to hours.
Why do highlighters glow under blacklight?
Their dyes are fluorescent — they absorb the UV in blacklight and re-emit it as bright visible light.