Clinical Scientists working in radiation safety need to have a good understanding of the quantities and units used in radiation safety to describe radiation exposure. These include measures of dose and radiation exposure. As the name suggests, phototherapy ultraviolet electromagnetic wave radiation is used to treat skin conditions. Lasers are widely used in many branches of medicine. They are widely used in ophthalmology, and as a cutting or ablating device in other forms of surgery in many specialisms such as urology and gynaecology and as a heating or curing device in other disciplines. Radiation effects can be divided into two distinct categories: stochastic – where the risk, or probability, of an effect is related to the level of exposure, and non-stochastic effects where direct injury can occur above a certain threshold dose. The International Atomic Energy Agency “Basic Safety Standards” document outlines standards for reducing unnecessary exposure to ionising radiation.