Types of Electromagnetic Radiation
The energy embodied in electromagnetic radiation depends on the frequency (or wave length) and/or amplitude (height) of the electromagnetic fields. The different frequencies of electromagnetic radiation are usually represented on a scale known as the electromagnetic radiation spectrum.
This scale may be divided into two main ranges, according to the amount of energy of the electromagnetic radiation, by frequencies: ionizing and non-ionizing radiation. This classification expresses the ability or non-ability of the radiation to cause changes in the physical structure of the atoms or molecules of matter.
Ionizing radiation
The range of high frequencies in the electromagnetic spectrum, whose lower limit lies within the ultraviolet light range, constitutes ionizing radiation. Electromagnetic radiation in this range of frequencies has the capacity to cause changes in the structure of atoms or molecules by ionization. In this case ionization refers to the ability of electromagnetic radiation to remove one or more electrons from the atoms or molecules. Following ionization, the atom becomes a positively-charged ion.
Non-ionizing radiation
The cluster of low frequencies in the electromagnetic spectrum whose upper limit lies within the ultraviolet light range is defined as non-ionizing radiation. It should be noted that visible light falls within this section. Non-ionizing radiation is incapable of causing structural changes in atoms or molecules by ionization. Conversely, although non-ionizing radiation does not have the ability to ionize atoms or molecules, it may affect the electronic behavior of matter through its electromagnetic fields (e.g. by influencing the polarization of atoms or molecules).
Ionization
Ionization refers to the capability of energy, such as that in electromagnetic radiation, to remove negatively-charged electrons from atoms or molecules. Each basic physical element (atom) is characterized by an ionization energy threshold. Energy stronger than this threshold may cause ionization of atoms, while weaker energy will not do so. Different materials have different ionization energy thresholds. Thus a specific energy level of electromagnetic radiation may be insufficient to cause ionization in one material, but may be sufficient in another.
References
- Medical-dictionary.thefreedictionary.com Search terms: Non-Ionizing Electromagnetic Radiation, Ionizing Electromagnetic Radiation, Ionization.
- Pawel Sowaa, Joanna Rutkowska-Talipskab, Urszula Sulkowskac, Krzysztof Rutkowskid. Ryszard Rutkowski. Ionizing and non-ionizing electromagnetic radiation in modern medicine, Polish Annals of Medicine 2012; 19:2:134–138.
- World Health Organization. What is Ionizing Radiation, available at http://www.who.int/ionizing_radiation/about/what_is_ir/en/. Last accessed 6 May 2015
- Australian Government, Australian Radiation Protection and Nuclear Safety Agency, Radiation Basics - Ionising and Non Ionising Radiation. Available at http://arpansa.gov.au/radiationprotection/basics/ion_nonion.cfm. Last accessed 6 May 2015