Invisible Highlighter Ink Under UV

1. Invisible Highlighter Ink Under UV Materials: Yellow highlighter marks; white paper; UV flashlight What you do: Compare marks under room light and UV. What students see: Some marks glow intensely. Question: Why is the glow brighter than the paper around it? 2. Tyndall Beam Appears in Dilute Milk Materials: 2 clear cups: water and very dilute milk; flashlight What you do: Shine beam through both from side. What students see: Beam path is much more visible in milk. Question: Why can we see the beam inside one liquid? 3. Invisible Glass in Oil Materials: Small clear glass object; clear oil with similar refractive index What you do: Lower the glass into the oil. What students see: Parts of the glass seem to disappear. Question: Where did the edge go?

Predict → observe three demonstrations → compare what changed → choose independent activity station → cleanup/share. Guiding questions: Question: Why is the glow brighter than the paper around it? Question: Why can we see the beam inside one liquid? Question: Where did the edge go?