Is the number on suncreen an indicator of how long it lasts, how much sun it can take or the percentage of rays it blocks? Or is it something else entirely?
In: Chemistry
The SPF number estimates roughly how long you can stay exposed to the sun while protected before absorbing the same dose of UV you’d get in an unprotected minute. So if a sunscreen is SPF 30 then in theory 30 minutes of sun with that protection is equivalent to one minute of sun without.
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