Waves Revision

Ultraviolet Radiation

Ultraviolet radiation comes in three categories, UVA, UVB and UVC. The letter denotes the amount of energy that the type of UV radiation carries - as such, it also tells us how harmful the radiation is to us as humans.

UVA is the least harmful type - it has the longest wavelength and carries the least amount of energy. UVA accounts for up to 95 percent of UV radiation that reaches the surface of the earth, and is thought to play a role in premature skin aging and wrinkling. Despite carrying less energy than UVB rays, they are far more prevalent, even throughout the winter months. They penetrate deeper than UVB rays, though do less harm, though some speculate they still exacerbate the risk of skin cancer.

UVB has a shorter wavelength, and carries more energy. It's responsible for burning, tanning, skin aging and the development of skin cancer. UVB rays hold the potential to ionise living cells in our skin - this strips away electrons from the nuclei of atoms, causing cancerous cells to develop. Its shorter wavelength means it can't penetrate the skin as deeply as UVA rays.

UVC rays are filtered out by the Earth's ozone layer - they have the shortest wavelength and the most amount of energy. UVC rays are germicidal (they kill microorganisms); hence they are often used to disinfect food, air and water. It is for this same reason that they are so harmful to human beings, because they effectively kill or inactivate cells. However, the likelihood of UVC rays penetrating skin is low, because of their extremely short wavelength.