you put sunscreen on before going to the beach but still end up getting burned, propose three rational hypothesis for why this might have occurred.
• Sunscreen's efficacy depends on sun protection factor, or SPF. It indicates how long it will take for UVB rays to redden skin when using a sunscreen, compared to how long skin would take to redden without the product. Long exposure to the sun without reapplying of sunscreen will cause sun burn. • Some sunscreens only protect against UVB radiation, and not against UVA component of the spectrum. Although UVB is the chief cause of skin reddening and sunburn, UVA rays account for up to 95 percent of the UV radiation reaching the Earth's surface. That’s why, the broad spectrum (UVA/UVB) sunscreen protects skin better. • Reduced exposure to UVB radiation supresses production of the natural photoprotector, melanin.