Revise GCSE Physics

Question:What does Sun Protection Factor mean?

The sun protection factor (usually abbreviated to SPF) is a number that tells us two things:

1.How much the UV exposure is reduced

2.How much longer you may be exposed to UV radiation before you will burn.

For example: Sun protection factor of 30 means that you can stay in the sun 30 times longer before you burn because the UV radiation actually hitting your skin had been reduced to one thirtieth of the level it would be at without the protection of the sunscreen.