Final answer:
Maximum skin exposure to UV light helps break down tightly bound molecules, and UV-B radiation can cause DNA damage and skin cancer. The ozone layer protects us from most UV-B light.
Step-by-step explanation:
Maximum skin exposure to ultraviolet (UV) light is needed to break down tightly bound molecules. UV light, specifically UV-B, can damage DNA and cause mutations, leading to skin cancer. The ozone layer in the atmosphere absorbs most of the UV-B light, but reductions in ozone levels can increase the amount of UV-B reaching the Earth's surface. Overexposure to UV-B radiation can be harmful to human health.