Which type of ultraviolet radiation is primarily responsible for sunburns?

The correct answer is UVB, as this type of ultraviolet radiation is primarily responsible for causing sunburns. UVB rays are more intense than UVA rays and directly affect the outer layer of the skin, leading to inflammation and skin damage, commonly known as sunburn. UVB radiation stimulates the production of melanin in the skin, which is the body’s natural defense mechanism against UV radiation, but excessive exposure can overwhelm this protection and cause burning.

In contrast, UVA rays penetrate deeper into the skin and can contribute to long-term skin aging and the development of skin cancer, but they do not cause sunburn in the same immediate way UVB rays do. UVC rays are mostly absorbed by the Earth's atmosphere and do not reach the surface, thereby not being a factor in sunburn. Infrared radiation (IR) is not ultraviolet and is primarily associated with heat rather than skin damage, further distinguishing its effects from those caused by UVB.