Black Light Fluorescence

Shine an ultraviolet (UV) “black light” on common items to reveal fluorescence. Students observe which materials glow and test mixtures (such as vitamins with vinegar) to explore how UV excitation produces visible light.

1. Darken the room and place sample items (white paper, petroleum jelly, tonic water or club soda, assorted vitamins, white vinegar) on a tabletop.
2. Turn on a UV flashlight and illuminate each item, noting any color changes or glow.
3. Crush small amounts of vitamins (e.g., riboflavin, thiamine, niacin, B12) in water to make test solutions; observe under UV.
4. Mix a small amount of vitamin solution with white vinegar and check again under UV to see if the glow or color changes.
5. Compare additional household items known to fluoresce (e.g., detergent-brightened fabrics, highlighter ink, some currency security features).

How Fluorescence Works - The Science - NurdRage:

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• Compare wavelengths: test a 365 nm “true UV” flashlight versus a 395–405 nm violet LED and note brightness differences.
• Make fluorescence art: draw on paper with petroleum jelly or highlighter, then reveal under UV.
• Test natural sources: tonic water (quinine), vitamin B2 (riboflavin), and chlorophyll extract (spinach in alcohol) for distinct colors.
• Contrast fluorescence vs phosphorescence using glow-in-the-dark plastic to discuss immediate vs delayed emission.

• Use only UVA/near-UV black lights intended for consumer use; avoid UV-C sources.
• Do not stare into the beam; limit direct eye and skin exposure. Consider UV-blocking glasses if sensitive.
• Handle vinegar and crushed vitamins carefully; avoid ingestion and contact with eyes. Label all mixtures and dispose properly.
• Protect surfaces and clothing from staining (highlighters, dyes). Wash hands after the activity.
• Keep small items and powders away from young children; supervise closely.

• Which items glowed most brightly, and what do they have in common? (They contain phosphors such as optical brighteners, quinine, or riboflavin that absorb UV and emit visible light.)
• Why does tonic water appear blue-white under UV? (Quinine fluoresces strongly in the blue.)
• Did mixing vinegar with certain vitamins change the glow? (Acidity can affect molecular form and fluorescence efficiency for some vitamins, notably B12 and riboflavin.)
• How is fluorescence different from phosphorescence? (Fluorescence stops almost immediately when the UV is removed; phosphorescence continues after excitation.)
• Where do we see fluorescence in everyday life? (Laundry brighteners, security features on money and IDs, forensic dyes, and some marine organisms.)