How long does UVA protection from sunscreen last?

Subject: How long does UVA protection from sunscreen last?

Date: Tue Jun 30 22:21:51 2009
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Area of science: General Biology
ID: 1246425711.Gb

Message:


I know that SPF is a measure of how much longer it would take someone to burn in the sun with UVB 
rays. 
If I typically burned within 10 minutes in the sun, SPF 15 would make that 150 minutes instead of 10. 
But 
that is just for UVB rays. How long does UVA protection last throughout the day, given any standardized 
measuring unit? Or does protection against UVA last all day, unlike  UVB protection?

Re: How long does UVA protection from sunscreen last?

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