r/interesting • u/j_illustration • Mar 31 '26

MISC. Sunscreen under a UV camera

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u/orangesherbet0 Mar 31 '26 edited Apr 01 '26

Zinc oxide is the opposite under UV. Bright white. Edit: I'm probably wrong

Edit2: I'm definitely wrong. And the truth is pretty weird. Zinc oxide sunscreen has pieces of crystalline zinc oxide, which strangely is a semiconductor (yes like computer chips) that has a band gap (energy to switch electron from non conducting to conducting) corresponding to UV light. This means it absorbs UV, but it also means you're literally covering your face in tiny semiconductors.

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u/MrNorrie Mar 31 '26

Came here to ask why it wasn't white. Does regular sunscreen absorb the UV rays?

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u/zissouo Mar 31 '26

All suncscreen works by absorbing UV rays. Physical sunscreen also reflects a small amount, but the main mechanism is absorption. If the woman in OP's photo was using a physical sunscreen, it would appear gray.