Ultraviolet (UV) radiation is a form of electromagnetic radiation with wavelengths shorter than those of visible light, but longer than X-rays. UV radiation occupies the portion of the electromagnetic spectrum between approximately 10 nanometers (nm) and 400 nm in wavelength.
UV radiation is categorized into three main regions based on wavelength:
UVA (315 nm to 400 nm): UVA radiation has the longest wavelengths among UV rays that reach the Earth's surface. It is often referred to as "long-wave" UV. UVA is less energetic than shorter-wavelength UV radiation, but it can still penetrate the Earth's atmosphere and reach the skin's deeper layers. UVA radiation is associated with skin aging, wrinkling, and some forms of skin cancer.
UVB (280 nm to 315 nm): UVB radiation has shorter wavelengths and higher energy than UVA. It is often called "medium-wave" UV. The Earth's atmosphere partially absorbs most of the UVB radiation, but a significant amount still reaches the surface. UVB is primarily responsible for sunburns, and prolonged exposure to UVB radiation increases the risk of skin cancer and can also affect the immune system.
UVC (100 nm to 280 nm): UVC radiation has the shortest wavelengths and the highest energy among UV rays. It is often called "short-wave" UV. UVC radiation is completely absorbed by the Earth's atmosphere and does not reach the surface. However, UVC radiation is used for various purposes in industrial and scientific applications, such as germicidal lamps for sterilization.
It's important to note that UV radiation from the sun can have both beneficial and harmful effects on living organisms. Controlled exposure to UVB radiation, for example, helps the human body synthesize vitamin D, which is essential for various physiological processes. However, excessive or unprotected exposure to UV radiation can damage DNA, cause sunburns, premature aging of the skin, and increase the risk of skin cancer. Hence, it is important to take appropriate precautions, such as wearing sunscreen, protective clothing, and sunglasses, to minimize the harmful effects of UV radiation.