What does SPF 30 provide compared to SPF 15?

SPF, or Sun Protection Factor, indicates the level of protection a sunscreen offers against UVB rays, which are the primary cause of sunburn and can contribute to skin cancer. An SPF 30 sunscreen provides more protection against UVB rays than an SPF 15 sunscreen. Specifically, SPF 15 blocks approximately 93% of UVB rays, while SPF 30 blocks about 97%. This increased percentage signifies a notable difference in the amount of UV radiation that reaches the skin. Therefore, choosing a higher SPF number essentially enhances the skin's defenses against potential sun damage, making it a more effective option for prolonged sun exposure.

The other options do not accurately represent how SPF ratings function. For instance, both SPF 15 and SPF 30 offer similar levels of UVA protection unless specifically marked as broad-spectrum. Application area or absorption rates are unrelated to SPF ratings directly, focusing more on the formulation and texture of the sunscreen rather than the SPF number itself.