Radiation



In physics, radiation is a process in which energetic particles or energy or waves travel through a medium or space. There are two distinct types of radiation; ionizingand non-ionizing. The word radiation is commonly used in reference to ionizing radiation only (i.e., having sufficient energy to ionize an atom), but it may also refer to non-ionizing radiation (e.g., radio waves, heat or visible light). The energy radiates(i.e., travels outward in straight lines in all directions) from its source. This geometry naturally leads to a system of measurements and physical units that are equally applicable to all types of radiation.

Both ionizing and non-ionizing radiation can be harmful to organisms and can result in changes to the natural environment. However, in general, ionizing radiation is far more harmful to living organisms per unit of energy deposited, because the ions produced cause DNA damage. Non-ionizing radiation is usually harmful or organisms only in proportion to the heat that it deposits. In contrast, ionizing radiation may destroy life at amounts of total energy absorbed (radiation absorbed dose) that deposit only inconsequential amounts of heat.