I see clothing that’s labeled UPF 50, but the clothing is basically transparent. The model’s bra shows through clear as day. How does such flimsy material block 98% of the sun’s rays?
In: Chemistry
UPF refers specifically to the ability to block UV light. Basically the material is transparent to visible light but not transparent to UV. The most common material we are familiar with that has those properties is glass, but there is no reason fabrics couldn’t.
I have glasses that block UV. I have printer paper that glows blue when hit by UV. I also have a strong UV-A flashlight. Shining the UV light onto the transparent glasses cause an almost completely dark shadow to appear on the paper behind it. Ergo, the glasses are only transparent to the wavelengths your eyes work with.
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