Final answer:
The top of the ears has the greatest risk for sunburn when the sun is directly overhead since they are directly exposed. Sunburn is caused by the damaging effects of UV radiation, particularly UV-B and UV-C. Protection against UV radiation with a high-SPF sunscreen is important to lower the risk of sunburn and skin cancer.
Step-by-step explanation:
If a person is walking outside with the sun directly overhead, the body part that has the greatest risk for sunburn is the top of the ears. This is because when the sun is directly overhead, the ears protrude from the side of the head and thus can be exposed more directly to the sun's rays compared to the forehead, nose, or chin, which may be angled and therefore could receive slightly less direct exposure. UV radiation from the sun can damage the outer layer of the skin, especially on parts directly exposed without any shade or protection.
Sunburn is a result of overexposure to ultraviolet (UV) light, particularly UV-B and UV-C wavelengths. Since UV light carries more energy than visible light, it is capable of breaking bonds at the cellular level, leading to skin damage like sunburn. Consequently, excessive UV exposure can increase the likelihood of developing skin cancer, with repeated sunburns escalating this risk. It’s critical to protect all exposed skin with sunscreen with a high sun protection factor (SPF), and possibly additional physical barriers such as hats and clothing, even when the sun doesn't seem as intense.