Definitions of Electromagnetic Frequencies, EMF, EMR, SAR, RF, Radio Waves, Microwaves
Definitions of Electromagnetic Radiation Terms
Our photo shows a collection of several types of radio transmit/receive antennas in Buenos Aires, Argentina.
Definition of EMF - an EMF or electromagnetic field is the field or area of force caused by movement of an electrical charge and containing some amount of electromagnetic energy.
Definition of EMR - Electromagnetic radiation, or electromagnetic radio frequency radiation EMFR. EMR or electromagnetic radiation is electrical and magnetic energy emitted by various types of energy sources: radio waves, microwaves, light, x-rays, and nuclear energy and sometimes expressed or measured in photons (particles) or as waves (discussed here).
EMR or EM radiation is the result of oscillating electrical and magnetic fields that move as an energy force in wave form through space.
Depending on the wavelength of a particular EMR source, it may be visible to the human eye (in the light spectrum).
While we provide more detailed definitions of types of EMR in this article, roughly EMR is divided according to its wavelength (in order of decreasing wavelength) into electrical energy (such as 60 cycle electrical current in a home, electrons oscillating in an electrical wire), radio waves, microwaves, visible light, ultraviolet light, x-rays, and gamma rays.
The higher the frequency of EMR the shorter is its wavelength. In general, electromagnetic radiation (EMR) is synonymous with electromagnetic waves.
Depending on wavelength, energy level, exposure, distance, and other factors, the biological effects of EMR may be heating (warming a chicken leg in a microwave oven), or ionization (knocking an electron off of a molecule to create an ion), to possibly profound effects on molecules or on cells of living tissue.
Definition of Ionizing radiation - ionizing radiation is electromagnetic waves powerful enough to change (ionize) molecules of a substance (human tissue, for example) that they strike.
Ionizing means creating an "ion" form of a molecule - that is, detaching an electron, converting the molecule to an "ionized" form with a different electrical charge. Ionizing radiation is known to be dangerous to humans and other animals.
It is the energy level of an electromagnetic wave that causes it to become ionizing, not the number of waves that occur. Short-wavelength (high frequency UV [ultra violet], X-rays, gamma rays) radiation is ionizing while low-frequency radiation is not.
Examples of ionizing radiation include high frequency radiation such as from X-rays, gamma rays, or nuclear radiation, alpha rays, beta rays, and neutrons from a nuclear reaction.
Definition of Non-ionizing radiation - low power non-ionizing radio waves at low levels of transmission power, such as older analog cell phone signals and cell phone radiation.
Definition of SAR & SAR Limits - Specific Absorption Rate of Radiation - measures the amount of radiation that a human body absorbs from a source such as from a nearby radio transmitting antenna or cellphone (radio receiving antennas do not emit EMF). In the United States the FCC requires that the SAR for cell phones is required to be no more than 1.6 watts per kilogram.
