How does sunscreen protect your skin from UV radiation?

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More specifically, does spf sunscreen work by reflecting UV or absorbing it?

I always assumed it reflected UV waves away from the body to protect the skin underneath, but then I see those “UV camera” photos where the sunscreen shows up dark which I was taught (if I remember correctly) means the sunscreen is absorbing all the UV and therefore not showing up on the image (no light being bounced into the lens). If it is being absorbed, does it disparate the energy somehow to stop it from harming the skin cells underneath? This has been bugging me for quite some time. Please help.

In: Physics