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Many words and phrases commonly used in EMF science are unfamiliar to most people. This can be a challenge for anyone trying to understand material  dealing with EMF issues. Below is my glossary of words and terms often used in EMF articles. This will be of help to you in understanding material found in books and on websites like this one. 


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ABSORPTION When the energy of an electromagnetic wave is dissipated in a substance, thus “absorbed”. Absorption results in heat, eddy currents or other anomalies in the absorbing material.

ACCURACY How close a measurement is to an established standard. For example an accuracy of +/- 5% means the reading is within 5% of an established laboratory standard

AMPERES The unit of measurement of electron flow in a conductor named after Andre Marie Ampere French mathematician and physicist of the 19th century.

ALTERNATING CURRENT An electric current (electrons) flowing through a conductor and alternating in direction so that the polarity (+ to -) continuously reverses direction at a regular interval of time. A graph of this current is called a periodic wave.

ATTENUATION Loss of amplitude or strength of a signal as it passes through a medium.

ARTIFICIAL EMR Electromagnetic radiation produced by man made technologies thus not natural to the environment.

BAND Not a music group, but a group (span) of frequencies allocated to some purpose. For example, the FM band is the group of frequencies allocated to FM radio stations from 88 MHz to 108 MHz

BIOELECTROMAGNETICS The study of the interaction of electromagnetic fields and biological systems. It also refers to the emerging field of medical therapies utilizing electromagnetism.

CURRENT An electric charge in motion through a conductive material.

deciBel (dB) a unit of measurement used to express very large or very small numbers based on logarithms (powers of 10).  Bel refers to the exponent while deci means 10ths. Thus, 1 Bel=10 deciBels. In mathematics positive exponents give positive numbers while negative exponents give fractions. For example:       One billion (1,000,000,000) can be written 109 or 90 dB             One billionth (1/1,000,000,000) can be written 10-9 or -90dB

DIRECT CURRENT An electric charge (electrons) flowing through a conductor in one direction.

DIRTY ELECTRICITY Electrical power (normally at 60 Hz U.S.) which has been contaminated with various harmonics and additional frequencies produced as a result of connected electrical equipment.

DYNAMIC FIELD An electric or magnetic field that is continuously changing in magnitude or frequency over time.

EDDY CURRENTS Swirling currents produced in a conductive material as an electromagnetic wave or dynamic magnetic field passes through it.

ELECTROMAGNETIC HYPERSENSITIVITY (EHS)   An undefined medical/psychological condition in which the sufferer claims to be hypersensitive to electromagnetic fields. Though the condition has not been scientifically established or falsified, the symptoms are real to the sufferer and therefore should be taken seriously. 

ELECTROPOLLUTION All the artificial electromagnetic radiation existing in the atmosphere at any given time.

ELECTROPHYSIOLOGY  The study and measurement of the electrical properties of cells and tissues  

EMF This acronym can designate any one of several things. On this website it is defined as Electro-motive force, one of the four fundamental forces of physics or (most often) electro-magnetic field – an area in free space where the electromagnetic force is present and measurable. The field may be static (not changing) or dynamic (varying continuously)

EMI Electromagnetic Interference - technically any unwanted interference in operation of an electronic device caused by an electromagnetic field from another source. The term has now been extended to refer to intermediate frequencies on the power line which originate from other sources such as electronic equipment. (see "dirty electricity")

EMR There are at least 12 definitions for this acronym!  On this website EMR is defined as electromagnetic radiation – a dynamic electromagnetic field which is propagated into space as a wave traveling at the speed of light (300 million meters per second)

FIELD region in space where a given effect (such as magnetism) exists

FREQUENCY The number of full cycles of a waveform per second given in Hertz (Hz)

GAUSS Unit of measurement of magnetic fields in the cgs system named after Johann Gauss a mathematician of the 19th century. The cgs system was replaced by the SI system in 1960 but the use of Gauss persists. 10,000 Gauss equals one Tesla.

GENOTOXIC Referring to a chemical that has the potential to cause genetic damage creating mutations in DNA. The term has been extended to refer also to anything which causes such damage including EMFs.

GEOPATHOLOGY A branch of medicine devoted to study of the relationship of geographic factors to the specifics of disease symptoms.

GIGA prefix used to indicate "Billions" and abbreviated using a capital G.  For example 5 GigaHertz  means 5 Billion Hertz usually written 5GHz

HARMONIC  An integer multiple of a fundamental frequency – that is the fundamental frequency times a positive whole number.

HERTZ The unit of measurement for frequency named after Heinrich Hertz the first person to prove the existence of electromagnetic waves.

IRRADIANCE The power of an electromagnetic wave received upon a surface and used as a measure of the intensity of the field. Usually given in Watts per square meter (W/m2) or smaller units thereof (eg mW/cm2)

ISOTROPIC WAVE An electromagnetic wave that is expanding away from a point source and is radiating equally in all directions. A pure isotropic source is theoretical only but is used as a comparison for field strength of other radiator configurations. The shape of real radiators (for example a wire) will tend to focus the wave in specific directions.

KILO prefix used to indicate "thousands" and abbreviated using a lower case k.  For example 5 kVolts  means 5 thousand  Volts usually written 5kV

MICRO A prefix used to indicate "millionths" and abbreviated using greek letter mu (u) For example 5 micro Watts means 5 millionths of a Watt  usually written 5uW

MILLI  prefix used to indicate "thousandths" and abbreviated using a lower case m.  For example 5 milliVolts  means 5 thousandths of a Volt usually written 5mV

MEGA A prefix used to indicate "millions" and abbreviated using a capital M.  For example 5 M Hertz means 5 Million Hertz usually written 5MHz

MICRO-WAVE There are many definitions of this term. Generally, the word “micro” means “small” and can refer to most any short wavelength EMR. This website restricts use to the technical definition: Electromagnetic radiation having frequencies in the spectrum between 1 gigahertz and 300 gigahertz encompassing the upper UHF, and all SHF and EHF bands and having wavelengths between 300 millimeters and 1 millimeter

MODULATION Altering a fundamental carrier frequency (EMR) in response to information. This allows the information to be detected at the receiver. There are three basic types of modulation – amplitude, frequency, and phase modulation.

NANO prefix used to indicate "billionths" and abbreviated using a lower case n.  For example 5 nanoWatts  means 5 billionths of a Watt usually written 5nW

NEAR FIELD Generally within one wavelength of an electromagnetic wave source. We use this definition though the technical definition depends on several other factors. For low frequencies such as 60 Hz a measurement taken anywhere will be near field because the wavelength is extremely long. The measured field will therefore be primarily magnetic in nature.

PERIOD The length of time for an A.C. voltage to complete one cycle through both positive and negative. Usually measured in fractions of seconds using metric units such as milliseconds, microseconds etc.

RADIATION There are different types of radiation. Unless otherwise specified on this website radiation refers to an electromagnetic wave propagating through the atmosphere

RADIATOR Any electrical conductor or device which radiates electromagnetic waves into the space around it.

REFLECTION Changing the path of an electromagnetic wave by bouncing off of a surface

REFRACTION Changing the path of an electromagnetic wave by bending it as it travels through media of different densities

RF   Radio frequency. This term has many definitions according to context. On this website we will use the most common definition: any frequency commonly used for electronic communication systems including frequencies from 3KHz (VLF) to 300 GHz (ELF).

SCHUMANN RESONANCE A natural resonant frequency of electromagnetic radiation in the atmosphere at around 7.8 Hz. This resonance is produced by the characteristics of the earth’s atmosphere and the circumference of the earth which acts as a waveguide for EMFs produced by lightning.

SI  System International - The international system of measurement which specifies units of measurement used for scientific research.

SIGNAL STRENGTH the strength of the signal as measured at a specific point in free space. The signal strength may be measured in Volts per meter (V/m) which is the voltage differential between two points in space which are one meter apart. Or, the power density of the signal on a given surface - for example micro Watts per square centimeter (uW/cm2)

SINEWAVE A waveform which when graphed as to how its amplitude varies with time shows a characteristic form based on the sine function (trigonometry) Sine waves are one fundamental frequency.

STATIC FIELD An electric or magnetic field which is fixed and not changing in magnitude or frequency over time.

RESONANCE   The vibration (oscillation) of a system at a specific frequency based on the mechanical or electrical characteristics of the system.

TESLA Unit of measurement for magnetic fields in the Scientific International (SI) system and named after Nicola Tesla scientist and inventor of the late 19th and early 20th century.  A one Tesla field is approximately that produced by some MRI machines.

VOLTAGE The force of attraction between positive and negative charges (pressure) which has the potential to move electrons if there is a path through which they can flow.

WATT The electrical unit of power named after Scottish engineer James Watt. One Watt is one Joule of energy used per second. An approximate equivalent is the amount of energy used by a 60W lightbulb in 1/60th second. In measuring EMRs units of milliWatts or microWatts are often used.

WAVE-LENGTH   The distance which an electromagnetic wave will travel through space during one complete cycle of the wave. The formula for wavelength is λ=300 M meters/f in a vacuum (where λ is wavelength and f is frequency). 300 M meters is the speed of light in a vacuum.

WI-FI Wireless fidelity – A technology standard used primarily for wireless local area networks in homes or businesses and utilizing 2.4GHz or 5Ghz bands.

Wi-Gig   Wireless Gigabit Alliance. A standard adopted in 2011 and merged with the Wi-Fi standard to provide high speed connectivity at up to 7 Gigabits per sec. and operating on the 60GHz band. More recently also on the 2,4, and 5GHz bands.

WI-MAX An international standard used for wireless connectivity for cell phones, internet, or other technologies and utilizing various channel frequencies with power capable of transmitting up to 30 miles.