The characteristic radiation arises from the electronic transition in an excited atom. Excitation is the removal of an electron from an inner shell. It requires energy that can be provided by fast electrons (such as in an X-ray tube or in a scanning electron microscope). Radiation is energy that comes from a source and travels through space at the speed of light.
This energy has an electric field and a magnetic field associated with it, and has properties similar to those of waves. Radiation could also be called “electromagnetic waves”. Radiation is the energy emitted by matter in the form of high-speed rays or particles. All matter is made up of atoms.
Atoms are made up of several parts; the nucleus contains tiny particles called protons and neutrons, and the outer shell of the atom contains other particles called electrons. The nucleus carries a positive electrical charge, while electrons carry a negative electrical charge. These forces within the atom work toward a strong and stable equilibrium by removing excess atomic energy (radioactivity). In that process, unstable nuclei can emit an amount of energy, and this spontaneous emission is what we call radiation.
Ionizing radiation has so much energy that it can expel electrons from atoms, a process known as ionization. Ionizing radiation can affect atoms in living things, posing a health risk by damaging the tissue and DNA of genes. Ionizing radiation comes from X-ray machines, cosmic particles from outer space, and radioactive elements. Radioactive elements emit ionizing radiation as their atoms undergo radioactive decay.
Unstable atoms are said to be radioactive. To achieve stability, these atoms emit or emit excess energy or mass. The types of radiation are electromagnetic (such as light) and particulate (i.e., gamma radiation and x-rays are examples of electromagnetic radiation). Gamma radiation originates in the nucleus, while X-rays come from the electronic part of the atom.
Beta and alpha radiation are examples of particle radiation that can be monitored with radiation detection badges.