UV (Ultraviolet) radiation is a type of electromagnetic radiation with a wavelength shorter than that of visible light but longer than X-rays. UV radiation is divided into three subcategories based on their wavelengths: UVA, UVB, and UVC.
UVA and UVB are the most common types of UV radiation that reach the Earth's surface, and they are the ones that have the most significant impact on human health. UVA has a longer wavelength and penetrates deeper into the skin, and is associated with skin aging and some types of skin cancer. UVB has a shorter wavelength and is the primary cause of sunburn and some types of skin cancer.
UVC, on the other hand, has a shorter wavelength than UVA and UVB, and it is completely absorbed by the Earth's atmosphere before it can reach the surface. Therefore, UVC radiation is not considered a significant risk to human health from natural sources. However, UVC radiation is often used for sterilization purposes, as it can kill bacteria and viruses by damaging their DNA.
In summary, the main difference between UV and UVC is their wavelength and the impact they have on human health. UV radiation is composed of UVA, UVB, and UVC, but UVC is not a significant risk to human health from natural sources and is primarily used for sterilization purposes. UVA and UVB, on the other hand, are the ones that have the most significant impact on human health and can cause skin damage, aging, and cancer.