How Can UPF Clothing Block Sunlight When the Clothing is See-Through?

Question

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

Answer 1

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.