Electromagnetic radiation and waves are a form of energy emitted and absorbed by charged particles which exhibits wave-like behavior as it travels through space. EM waves have electric and magnetic field components, which stand in a fixed ration of intensity to each other, and which oscillates in phase perpendicular to each other and perpendicular to the direction of energy and wave propagation. In a vacuum, electromagnetic radiation travels at the speed of light.
Electromagnetic radiation is a form of electromagnetic fields which is produced by moving charges. It is associated with EM fields that are far enough away from the moving charges that produced them. It carries energy through space continuously away from the source. It also carried both momentum and angular momentum. These properties are important to matter with which it interacts.
In classical physics, ER is considered to be produced when charged particles are accelerated by forces acting on them. The electrons are responsible for emission of most EMR due to their low mass which makes them easily accelerated by a variety of mechanisms. Quantum processes can also produce EMR. This can happen when atomic nuclei undergo gamma decay and processes such as neutral pion decay.
The effects of EMR on biological systems depend upon the radiation’s power and frequency. Lower frequency of EMR up to visible light have damage determined by the heating effects and thus by the radiation power. In contrast, for higher frequency radiation at ultraviolet frequencies and above can damage the chemical materials and living cells by EMR is far larger than that done by simple heating. This is due to the ability of single photons in such high frequency EMR to damage individual molecules chemically.