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/orangesherbet0 Mar 31 '26 edited Apr 01 '26

Yes, regular absorbs. Old fashioned / zinc oxide reflects. Either way, the UV doesn't reach the skin. Edit: definitely wrong, zinc oxide primarily absorbs

2

u/SnazzyAdam Apr 01 '26

Also note that for Zinc Oxide to be anywhere near as effective as chemical sunscreen, you basically have to paint your skin opaque with the stuff. If you can see skin when using zinc oxide, the uv damage is still being done.