- Albert Einstein
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Glossary
A B C D E F G H I K L M N O P Q R S T U V W
If you can't find it here, try Miriam Webster
- Absolute temperature scale
- Another name for the Kelvin scale; absolute zero is denoted by 0°K.
- Absolute zero
- The lowest possible temperature according to the kinetic theory; all molecular motions cease.
- Acceleration
- The change in instantaneous velocity divided by the time interval over which the change occurs.
- Acceptable risk
- The cost in human life is justified, given the economic benefit.
- Action and reaction, law of
- (Newton's third law) When A exerts a force on B, B will exert a force on A equal in magnitude but opposite in direction to the force which A exerts on B.
- Aether
- The medium hypothesized by nineteenth-century physicists for the propagation of light; relative to an observer at rest with respect to the aether, the speed of light was thought to be c = 3 x 108 m/sec.
- Alternating current (AC)
- An electrical current that changes its direction of flow with a certain periodicity. For example, 60-cycle AC is an electrical current that changes its direction of flow 60 times per second. Also loosely used as a synonym for any current or field that varies with time.
- Ampere (Amp, A)
- Unit of measurement for electric current; 1 ampere equals the flow of one coulomb of charge each second past a fixed point. Represented in electrical equations as I, related to Voltage (V), and Resistance (R), as described by Ohm's Law: I = V/R.
- Amplitude
- The maximum displacement of a wave.
- Analytic statement
- A statement which says nothing about the physical world; e.g., "The fleen is prang" or "A triangle contains 180 degrees."
- Angstrom
- A unit of length often used for wave-lengths; 1 A = 10-10 meters.
- Angular acceleration
- The change in the instantaneous angular velocity divided by the time over which the change occurs.
- Angular displacement
- The change in angle of an object moving in a circle; usually measured in radians.
- Angular momentum
- Defined by the equation L = r x mv; in a circle. we have the simple form L = mvr.
- Angular speed
- The scalar part of angular velocity.
- Angular velocity
- The angular displacement divided by the time over which the displacement occurs; direction given by a right-hand rule.
- Antimatter
- A general term for the collection of antiparticles.
- Antinode
- A point of maximum wave displacement in a standing wave pattern..
- Antiparallel
- Pointing in opposite directions, usually referring to vectors, e.g., north and south, east and west.
- Antiparticle
- General term for a particle with internal quantum numbers which are the negative of those of the corresponding particle.
- A posteriori statement
- A statement whose truth or falsity depends on appeal to experience.
- A priori statement
- A statement whose truth or falsity depends on an appeal to reason, not experience.
- Area rule
- On a velocity-vs.-time graph, the area under the curve gives the distance traveled.
- Atom
- The smallest particle of matter into which an element can be resolved by chemical means; retains the same chemical properties as the original element.
- Atomic number
- The number of protons or positive charges in a nucleus; appears as a subscript to the left of the element symbol.
- Atomic weight
- The average of the mass numbers of the isotopes found in a large, naturally occurring sample of an element.
- Average (temporal) power
- The time-averaged rate of energy transfer.
- Average value of a physical variable
- The change in the variable over a finite time period; if the variable changes uniformly over the time interval, the average value is equal to the instantaneous value of the variable.
- Averaging time
- The appropriate time period over which exposure is averaged for purposes of determining compliance with RF exposure limits.
- Avogadro's hypothesis
- Equal volumes of gas at the same temperature and pressure contain the same number of molecules or atoms.
- Axiom
- A basic assumption underlying a theory or branch of mathematics.
- Big-bang model
- A theory in cosmology according to which our present expanding universe arose from an initial explosion of a small compact mass of matter.
- Bilateral
- Term applied to the symmetry of a figure; usually means that the left-hand side is the mirror image of the right-hand side.
- Blastema
- The mass of primitive, embryonic cells appearing at the site of injury in an animal capable of regeneration. These cells subsequently grow and form a replica of the missing part.
- Bohr model
- An outdated theory of the hydrogen atom in which electrons follow discrete circular orbits about the proton.
- Brownian motion
- The random, zigzag motion of a particle suspended in a liquid or gas; caused by molecular impacts.
- Caloric
- The substance responsible for heat, according to an archaic theory.
- Calorie
- An energy unit used to measure heat; 1 Calorie = 4.186 joules. (There are TWO types of calories: the Calorie = 4.186 J, and the kilocalorie, aka: Nutritional Calorie = 4186 J.)
- Carcinogenic
- A substance or force capable of causing a cancer.
- Centigrade temperature scale
- A temperature scale on which ice melts at 0°C and water boils at 100°C.
- Centripetal acceleration
- The acceleration which acts toward the center of the circle on an object in uniform circular motion; its magnitude is a = v2/r where v is the speed and r is the radius of the circle.
- Centripetal force
- The product of centripetal acceleration and the mass of the object in uniform circular motion.
- CGS units
- Units of measurement based on the centimeter, gram, and second.
- Charge, electric
- A fundamental, irreducible property of some elementary particles; measured in coulombs. "The electrical property of matter that's responsible for creating electric fields." Either positive or negative.
- Circadian rythm
- The biological cycle that usually occurs at 24-hour intervals and is also known as the biological clock. Believed to be tied to the Schumann Resonance.
- Circuit
- A system of electric conductors that will allow a flow of current.
- Closed system
- A system of interacting entities such that nothing either enters or leaves the system.
- Commutative
- Two operators or operations are said to be commutative if the result of the first applied before the second is the same as that of the second applied before the first.
- Commutator
- [A, B] = AB - BA.
- Component of a vector
- One of a pair of (perpendicular) vectors whose resultant is the given vector.
- Conservation law
- A general law requiring that a physical variable have the same value at a later time as at some earlier time.
- Constant
- (a) A fixed number, (b) unchanging or uniform.
- Continuous
- A collection is continuous if for any given member of the set there does not exist another element "closest" to the original member; e.g., the real numbers from 0 to 1.
- Continuous exposure
- Exposure for durations exceeding the corresponding averaging time. Applicable in applying exposure standards.
- Correspondence principle
- Principle that a new theory must make the same predictions as an older theory in those circumstances in which the older one is known to be correct (due to Niels Bohr).
- Cosine
- The ratio of the side adjacent to an angle to the hypotenuse of a right triangle; corresponds to the x-component of a unit vector.
- Cosmological principle
- Principle which states that what we observe of the expansion of the universe will also be observed by any other observer in the universe.
- Coulomb
- The unit of measurement for electric charge; 1 coul is equivalent to the charge of 6.25 X 1018 electrons.
- Coulomb's law
- The basic equation for the interaction between electric charges, F = KqQ/r2
- Crest
- The highest point on a sinusoidal wave.
- Current, electric
- The flow of charge, measured in amperes, amps, A.
- Cyclotron
- An accelerator for elementary particles in which the charged particles follow circular paths in a uniform magnetic field.
- De Broglie's relation
- The equation for the matter wavelength, lamda = h/P, where h = Planck's constant and P = linear momentum.
- De Broglie wavelength
- The wavelength of matter waves.
- Decibel (dB)
- Ten times the logarithm to the base ten of the ratio of two power levels. Frequently used to describe power levels when evaluating antennae.
- Deferent
- The large circle, centered on the earth, on which the epicycle rotates according to the geocentric astronomical theory.
- Delta
- Name for the symbol
denoting the change in some physical variable - final value minus initial value.- Derived Quantities
- A simple example is velocity, as a combination of the basic dimensions of length and time. The units can be feet per second, meters per second, or centimeters per second, volts per meter. Still, basically velocity is just L/T meaning it is the time rate of change of length. Sometimes speed and velocity are used interchangeably. However, velocity is a vector quantity that has direction, while speed is a scalar quantity without direction. Another derived quantity is acceleration, the time rate of change of velocity. In the mks and SI systems the unit is meters per second per second, or m/s2. The basic dimensions are L/T2, which results from L/T for velocity, divided by T. Additional derived quantities are force, work or energy, and power.
- Diatomic
- Composed of two atoms.
- Direct current (DC)
- An unvarying or steady electrical current. Also used as a synonym for any unvarying or steady-state process, such as a DC magnetic field.
- Direction of electric field
- Direction in which a positive test charge would move if placed at the point in question.
- Direction of magnetic field
- Direction in which the north pole of a compass would point if placed at the point in question.
- Discrete
- A collection is discrete if for any given element there exists another member of the set "next to" the original element; e.g., the whole numbers.
- Displacement
- The change in position of an object (a vector).
- Distribution line
- A power line used to distribute power locally to a Utilities end-users.
- Doppler effect
- The phenomenon in which the frequency of a wave is changed by the motion of the source and/or the observer.
- Duty factor
- The ratio of pulse duration to the pulse period of a periodic pulse train. Also, may be a measure of the temporal transmission characteristic of an intermittently transmitting RF source such as a paging antenna by dividing average transmission duration by the average period for transmissions. A duty factor of 1.0 corresponds to continuous operation.
- Dynamics
- The study of the forces or causes of motion.
- Effective radiated power (ERP) (in a given direction)
- The product of the power supplied to the antenna and its gain relative to a half-wave dipole in a given direction.
- Equivalent Isotropically Radiated Power (EIRP)
- The product of the power supplied to the antenna and the antenna gain in a given direction relative to an isotropic antenna.
- Electric charge
- A fundamental, irreducible property of some elementary particles; measured in coulombs.
- Electric current
- The flow of charges; measured in amperes, (amps, A).
- Electric field
- A vector defined as the electric force exerted on a positive test charge divided by the magnitude of the positive test charge.
- Electric field strength (E)
- A field vector quantity that represents the force (F) on an infinitesimal unit positive test charge (q) at a point divided by that charge. Electric field strength is expressed in units of volts per meter (V/m).
- Electric force
- The attraction or repulsion of charged objects, usually elementary particles; the mathematical formula for electric force is Coulomb's law.
- Electric potential
- The work which must be done to move a positive test charge from one point to another in an electric field divided by the magnitude of the test charge; measured in volts.
- Electric potential energy
- The work we must do to move a positive test charge from one point to another in an electric field; for point charges, PE = KqQ/r, where r is the distance between centers and K = 9 x 109 nt-m/coul2.
- Electromagnetic field (EM field)
- A force field that extends or radiates out away from any moving electrical current. This electromagnetic field has a direction of movement away from the electrical current and contains both a magnetic field and an electric field.
- Electromagnetic spectrum (EM spectrum)
- A way of organizing electromagnetic fields on the basis of their frequency of oscillations. The non-ionizing electromagnetic spectrum starts with zero (no oscillation, or DC) and extends up to visible light with trillions of oscillations per second. Frequencies of oscillation above light are considered to be ionizing and include X-rays and cosmic rays. The EM spectrum is divided into regions based on frequency and usage. See also Extra low frequency, Very low frequency, Radio frequency, and Microwave.
Thanks to the folks at NoRad for allowing me to use their chart, ©;NoRad Corporation, 1998- Electromagnetic wave
- A wave which travels at the speed of light and is characterized by oscillations of combined electric and magnetic fields; examples are light, radio waves, x-rays.
- Electron volt
- The energy change experienced by an electron when passing through a potential difference of one volt; also applicable to any particle with a charge of the same magnitude as the electronic charge, the smallest unit of charge; denoted by eV; 1 eV = 1.6 X 10-19 joule.
- Ellipse
- A geometric figure defined by the distance of any point on the curve from two fixed points, called the foci; if o and b are the two distances, then o + b = constant.
- EMF
- Electromagnetic field
- Empiricism
- Philosophical position that all knowledge is derived from experience.
- EMR
- Electromagnetic radiation
- Energy
- A physical variable measured in joules; we say that an object gains or loses energy when work is done on the object; conversely, an object has energy if it can do work on another object. Energy is the ability to do work. Kinetic energy is due to the motion of a mass, as when you throw a ball. Potential energy is stored energy, as in a coiled spring. The units for both kinetic and potential energy are the same as for work. (See Work.)
- Energy density (electromagnetic field)
- The electromagnetic energy contained in an infinitesimal volume divided by that volume.
- Energy level
- The discrete values of energy for a quantized system.
- Energy level diagram
- A diagram in which the energy levels for a quantum system are displayed; levels represented by straight horizontal lines arranged vertically.
- Epicycle
- The small circle rotating on the deferent on which a planet moves in the geocentric system of astronomy.
- Epidemiology
- The study of the distribution of disease in populations.
- Equal areas, law of
- Kepler's second law of planetary motion: the line joining a planet to the sun sweeps out equal areas in equal times.
- Equation of motion
- An integral part of any dynamical system which relates the acting forces to the motion of the system.
- Equivalence principle
- The assumption that an accelerated observer in a gravity-free region is equivalent to an observer at rest in a gravitational field; due to Einstein.
- Euclidean geometry
- The usual geometry of a flat surface; plane geometry.
- Event
- A point in space-time defined by two numbers, its spatial distance and its temporal distance from a reference event, usually the origin 0 of the space-time diagram.
- Expanding universe
- A theory that the red-shift in the spectrum of galaxies is due to the recession of the galaxies from our location in the universe.
- Exposure
- Exposure occurs whenever and wherever a person is subjected to electric, magnetic or electromagnetic fields other than those originating from physiological processes in the body and other natural phenomena.
- Exposure, partial-body
- Partial-body exposure results when RF fields are substantially nonuniform over the body. Fields that are nonuniform over volumes comparable to the human body may occur due to highly directional sources, standing-waves, re-radiating sources or in the near field. See RF "hot spot".
- Extra low frequency (ELF)
- The portion of the electromagnetic spectrum extending from zero to 1000 cycles per second. This includes the 60-cycle power frequency in the United States, the 50-cycle European power frequency, and the U.S. Navy's submarine communication system at 45 and 75 cycles per second.
- Fahrenheit temperature scale
- Temperature scale on which the melting point of ice and the boiling point of water are 32°F and 212°F, respectively.
- Far-field region
- That region of the field of an antenna where the angular field distribution is essentially independent of the distance from the antenna. In this region (also called the free space region), the field has a predominantly plane-wave character, i.e., locally uniform distribution of electric field strength and magnetic field strength in planes transverse to the direction of propagation.
- Field
- The area around a source of electric or magnetic energy within which a force exists and can be measured. This is sometimes termed radiation in the sense that electromagnetic fields radiate out and away from the source and have characteristics of particulate radiation (see Photon).
- First law of thermodynamics
- Statement that energy is conserved when heat is considered as one form of energy: often also includes chemical energy.
- Fission
- A type of nuclear reaction in which a nucleus with a large atomic number breaks into two or more smaller-atomic-number nuclei with the release of energy; reaction used in the atomic bomb and atomic power plants.
- Focus
- One of the two points which define an ellipse; the sun is at one focus of planetary ellipses; plural is foci.
- Force
- The product of mass (m) and acceleration (a), measured in newtons (nt); thought of as the cause of motion in classical dynamics; that quantity which equals ma in Newton's equation of motion; e.g., gravitational force or the Lorentz force law. Newton's law of acceleration is used to derive the units of force. With the formula F = Ma in the cgs system, one dyne is the force needed for an acceleration of one centimeter per second per second with a mass of one gram. In the mks and SI systems, one newton is the force needed for an acceleration of one meter per second per second with a mass of one kilogram. One newton equals 105 dyne. To convert to English units, 1 N = 0.225 lb.
- Foucault's pendulum
- A pendulum used to establish the rotation of the earth; at the north pole a pendulum rotates 360° in one day.
- Free particle
- A particle which fulfills the conditions set forth in the principle of inertia.
- Frequency
- The number of waves passing a fixed point in one second; measured in hertz (Hz); 1 Hz = 1 cycle/second. The inverse of period.
- Fusion
- A type of nuclear reaction in which elements with small atomic numbers are combined to produce an element with a larger atomic number with the release of energy; usually involves hydrogen nuclei combining to form helium nuclei; also called thermonuclear reactions; responsible for the energy output of the sun and other stars.
- Gain (of an antenna)
- The ratio, usually expressed in decibels, of the power required at the input of a loss-free reference antenna to the power supplied to the input of the given antenna to produce, in a given direction, the same field strength or the same power density at the same distance. When not specified otherwise, the gain refers to the direction of maximum radiation Gain may be considered for a specified polarization. Gain may be referenced to an isotropic antenna (dBi) or a half-wave dipole (dBd).
- Galactic red-shift
- Shift in the spectrum of galaxies toward the red end of the spectrum; usually interpreted as due to recession of the galaxies (a Doppler effect).
- Galaxy
- A large collection of stars separated by vast distances from other such collections.
- Gauss
- CGS unit of measurement for magnetic fields; usually milligauss (mG) is used, 1/1000 of a Gauss. 10 mG = 1 µT, (micro Tesla.)
- Gauss meter
- A device used to measure magnetic flux density, or the "strength" of a magnetic field.
- Gene
- A portion of DNA that determines a specific characteristic. See also Oncogene.
- General population/uncontrolled exposure
- For FCC purposes, applies to human exposure to RF fields when the general public is exposed or in which persons who are exposed as a consequence of their employment may not be made fully aware of the potential for exposure or cannot exercise control over their exposure. Therefore, members of the general public always fall under this category when exposure is not employment-related.
- General theory of relativity
- Einstein's relativity theory extended to include accelerated observers and gravitation, via the equivalence principle.
- Geocentric
- Word to describe astronomical systems assuming that the earth is the primary point of reference for celestial motions; earth-centered.
- Geometric symmetry
- General term for the symmetries displayed by geometric figures, such as circles, squares, hexagons, etc.
- Gravitational acceleration
- At the earth's surface all objects with mass accelerate downward at the rate g = 9.8 m/sec per sec; for an object separated from a mass M by a distance r, the gravitational acceleration is ag = GM/r2.
- Gravitational constant
- Denoted by C; appears in the equation for gravitational potential energy (-GmM/r) and the equation for gravitational force (GmM/r2); G = 6.67 X 10-11 nt-m2/kg2.
- Gravitational mass
- The mass which appears in the law of universal gravitation; the property of an object which governs bow the object partici-pates in gravitational interactions.
- Gravitational red-shift
- Change in the frequency of light due to gravity.
- Half-life
- The time required for a large sample of a decaying system (radioactive substance, elementary particle) to lose its mass by one half.
- Harmonic law
- Another name for Kepler's third law of planetary motion.
- Heat
- In the cgs system, one calorie is the amount of heat needed to raise the temperature of one gram of water by one degree Celsius. In mks units, the amount of heat to raise the temperature of one kilogram of water by one degree Celsius is equal to one kilocalorie. The SI system uses the joule as a unit of heat as well as a unit of work. In English units, the British thermal unit (Btu) is the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit. The Btu is the larger unit, as 1 Btu equals 252 calories. The fact that heat is a form of energy can be seen from the use of the joule; 1 calorie is equivalent to 4.19 J. One joule equals 0.24 calorie.
- Heliocentric
- Word describing astronomical systems based on the sun as the primary reference frame for the description of planetary motions; sun-centered.
- Hertz (Hz)
- The frequency of electromagnetic radiation in cycles per second. One Hz is one cycle per second. One thousand cycles per second is 1 kHz. One million cycles per second is I MHz. One billion cycles per second is I GHz. Hz is derived from Heinrich Hertz, who discovered electromagnetic radiation.
- Homogeneous
- The same throughout; when applied to space and time, means that where a closed system is located in space or when an experiment is performed on the closed system has no effect on the experimental outcome.
- Hormone
- A chemical produced by glands in the body that controls cellular functions and transmits messages from the brain to the cells.
- Indeterminacy principle
- Another name for the uncertainty principle.
- Index of refraction
- The ratio of the speed of light in air (vacuum) to the speed of light in a particular medium; denoted by N with a subscript to indicate the medium.
- Induction
- Term denoting the process by which an object becomes electrically or magnetically polarized, i.e., one end becomes + and the other - or one end a north pole and the other end a south pole.
- Induced current
- The electric current produced in a conductor when the conductor is moved through an external magnetic field; or when the stationary conductor is in an expanding and collapsing magnetic field, like AC.
- Inertia, principle of
- Definition of a free particle; a free (noninteracting) particle is completely described by the constancy of its velocity.
- Inertial mass
- The mass of an object as determined by our basic operational definition of mass; the property of an object which appears in Newton's equation of motion, F = ma.
- Interaction
- A general term to express the fact that one object is affected by another; the effect that one object has on another (gravitational interaction, etc.).
- Interacting particle
- A particle which is not free.
- Interference
- General wave phenomenon in which one wave combines with another (the superposition principle) to produce a wave radically different from those combined.
- Internal symmetry
- A symmetry of elementary part ides not related to space and time; responsible for the internal conservation laws.
- Intrinsic angular momentum
- Spin or Spin angular momentum.
- Invariant
- Unchanging.
- Ion
- An atom that has lost or gained one or two electrons so that it has an electrical charge and is chemically much more active than the neutral ion, which has a balance of positive and negative charges.
- Ionization energy
- The energy required to remove an electron completely from an atom.
- Ionized
- Generally means that an atom has lost one (singly ionized) or more electrons.
- Ionizing
- The production of ions from neutral atoms by exposure to radiation with sufficient strength to dislodge electrons.
- Isotopes
- Two atoms of the same element but having different numbers of neutrons in the nucleus are called isotopes.
- Isotropic
- Same in all directions; the isotropicity of space means that the outcome of an experiment performed on a closed system does not depend on the orientation of the closed system.
- Kelvin temperature scale
- Temperature scale on which the boiling point of water and the melting point of ice are 373°K and 273°K, respectively; 0°K is known as the absolute zero.
- Kepler's third law
- The harmonic law which states that the ratio of mean distance cubed to period squared (R3/T2) is the same for all objects revolving around the same central gravitating mass.
- Kilovolt (kV)
- 1,000 Volts. The Volt is unit for measuring electrical potential, or "pressure."
- Kinematics
- Study of the description of motion.
- Kinetic energy
- Energy of motion, given by mv2/2.
- Kinetic theory
- Physical theory based upon a description of gases in terms of the kinematics and dynamics of particles in rapid random motion.
- Laplacian determinism
- View that the universe is completely determined so that given the forces of nature, Newton's equation of motion, and knowledge of the present state of matter, the future and past of any system can be precisely calculated.
- Leukemia
- Cancer of the blood tissue.
- Light year
- Astronomical unit of distance equal to the distance light travels in one year (9.5 x 1015 m).
- Linear momentum
- Physical variable defined by P = mv.
- Linear particle accelerator
- A device used to accelerate elementary particles to high energies and to speeds close to the speed of light; particles accelerated in a straight line by a large number of small accelerations.
- Longitudinal wave
- A wave in which the oscillations are parallel to the direction of motion of the wave, like a sound wave.
- Magnetic bottle
- Bottle-shaped magnetic fields to confine charged particles.
- Magnetic field
- Intermediary for the transmission of the magnetic force; denoted by B.
- Magnetic field strength (H)
- A field vector that is equal to the magnetic flux density divided by the permeability of the medium. Magnetic field strength is expressed in units of amperes per meter (A/m).
- Magnetic force law
- F = qv x B.
- Magnetite
- A naturally occurring mineral that is magnetic. Frequently occurs in biological organisms that utilize magnetic information for survival. Newts and Homing Pigeons, for example, are believed to use structures containing magnetite to navigate.
- Magnitude of a vector
- The length of a vector when represented by an arrow; the scalar part of a vector.
- Mass
- The dimension of mass is often considered similar to the weight of an object. However, weight is actually the force due to the acceleration of gravity. To define mass more specifically, it is necessary to use Newton's second law of motion: F = Ma. This can be transposed to M = F/a, which states that the mass is defined by how much force is necessary for a given amount of acceleration.
- Mass number
- The number of neutrons and protons in a nucleus.
- Matter
- A general term for the material stuff in the universe; often does not include antiparticles.
- Matter wave
- A wave used to describe elementary particles; specified mathematically by de Broglie's relation.
- Matter wavelength
- The wavelength of matter given by de Broglie's relation.
- Maximum permissible exposure (MPE)
- The rms and peak electric and magnetic field strength, their squares, or the plane-wave equivalent power densities associated with these fields to which a person may be exposed without harmful effect and with an acceptable safety factor.
- Maxwell's equations
- The equations expressing the sources and interactions between electric and magnetic fields.
- Mechanical energy
- The sum of potential energy and kinetic energy.
- Mechanical equivalent of heat
- The conversion factor between heat units and energy units; 1 Calorie = 4.186 joules, (one kilocalorie, or nutritional calorie is equal to 4186 joules.)
- Melatonin
- A hormone produced by the pineal gland that regulates the level of activity in the brain.
- Micropulsations
- Components of the Earth's Natural Geomagnetic Field, that are now believed to be responsible for phenomena such as your "biological clock.".
- Microwave
- That portion of the electromagnetic spectrum extending in frequency from 500 million cycles per second (500 MHz) up to the frequencies of visible light.
- Mitosis
- The process of cell division.
- MKS units
- Units of measurement based on the meter, kilogram, and second.
- Molecule
- A particle made up of two or more atoms.
- Momentum
- Linear momentum, mv.
- Monatomic
- Made up of only one atom.
- Monopole
- (a)A single north or south magnetic pole (not found in nature). (b)Tower A structure used to place antennas, fabricated as a single pole, (not previously found in nature.)
- Multiple proportions, law of
- Statement that when atoms combine, they combine in the ratio of simple whole numbers.
- Near-field region
- A region generally in proximity to an antenna or other radiating structure, in which the electric and magnetic fields do not have a substantially plane-wave character, but vary considerably from point to point. The near-field region is further subdivided into the reactive near-field region, which is closest to the radiating structure and that contains most or nearly all of the stored energy, and the radiating near-field region where the radiation field predominates over the reactive field, but lacks substantial plane-wave character and is complicated in structure For most antennas, the outer boundary of the reactive near field region is commonly taken to exist at a distance of one-half wavelength from the antenna surface.
- Necrosis
- The dissolving of dead tissue or cells.
- Neuroepidermal junction
- A structure formed from the union of skin and nerve fibers at the site of tissue loss in animals capable of regeneration. The structure produces the specific electrical currents that bring about the subsequent regeneration.
- Newtonian synthesis
- The resolution of the differences between terrestrial and celestial physics which existed before Newton's Principia; also the synthesis of rationalism and empiricism in the Newtonian paradigm.
- Newton's first law
- The principle of inertia.
- Newton's second law
- Newton's equation of motion F = ma.
- Newton's third law
- The law of action and reaction.
- NIEMR
- Non-Ionizing ElectroMagnetic Radiation
- Nodal line
- A line along which waves combine to produce only nodes.
- Node
- A point where the amplitude of a wave or of a sum of waves is zero.
- Noncommunicative
- Not communicating; members of the greater EMF research community.
- Noncommutative
- Not commutative.
- Noneuclidean geometry
- Geometry for a surface which is not flat, e.g., the surface of a sphere or saddle.
- Noninertial
- Accelerated.
- Nonionizing radiation
- That part of the electromagnetic spectrum extending from zero frequency to the frequencies of visible light. This radiation does not contain sufficient intrinsic energy to cause ionization of atoms in the body's chemicals.
- Nonunion
- A fracture of a bone that has failed to heal.
- Nuclear model
- (of an atom) View that an atom is largely empty space with essentially all the mass concentrated in a small region called the nucleus; the nucleus is enveloped by One or more electrons.
- Nucleon
- A proton or a neutron.
- Nucleus
- The central mass in an atom containing protons and neutrons.
- Observer
- A person or recording instrument receiving and recording information about physical events.
- Occupational/controlled exposure
- For FCC purposes, applies to human exposure to RF fields when persons are exposed as a consequence of their employment and in which those persons who are exposed have been made fully aware of the potential for exposure and can exercise control over their exposure. Occupational/controlled exposure limits also apply where exposure is of a transient nature as a result of incidental passage through a location where exposure levels may be above general population/uncontrolled limits (see definition above), as long as the exposed person has been made fully aware of the potential for exposure and can exercise control over his or her exposure by leaving the area or by some other appropriate means.
- Oncogene
- One or more genes that produce cancer. These genes are normally repressed, but a variety of factors can cause their activation, including virus infections, carcinogenic chemicals, and nonionizing and ionizing radiation.
- Operational definition
- A definition which tells how the thing defined can be measured or discovered experimentally.
- Operationalism
- Viewpoint that all aspects of physical theory must be expressible in direct physical terms, i.e., in measurement or observations.
- Operator
- A mathematical object used to describe some operation.
- Optic axis
- Direction in a polaroid filter which determines the polarization direction of light passing through the filter.
- Oscillatory motion
- Simple harmonic motion; the motion of the projection onto the x-axis of a point undergoing uniform circular motion.
- Osteomyelitis
- Infection of bone.
- Paradigm
- General viewpoint in science which indicates how and which phenomena are to be described and investigated.
- Particle
- A point moving through space.
- Peak Envelope Power (PEP)
- The average power supplied to the antenna transmission line by a radio transmitter during one radiofrequency cycle at the crest of the modulation envelope taken under normal operating conditions.
- Perihelion
- Point of closest approach of a planet to the sun; also applies to the point of closest approach of any body orbiting around another.
- Perineural cell
- One of several types of cells that surround nerve cells.
- Periodic function
- A quantity which after an interval (of space or time) repeats itself exactly.
- Periodic table
- An ordering of the chemical elements by rows and columns according to the filling of electrons in energy shells; also related to atomic numbers and the chemical properties of elements.
- Phase
- A labeling of points on S sinusoidal wave given by the angle of the corresponding sine function.
- Photoelectric effect
- Phenomenon in which light causes the ejection of electrons from a surface.
- Photoelectric equation
- An equation developed by Einstein for the energy balance in the photo-electric effect: hv = (0.5 * mv2) + w where hv is the light energy, w is the maximum energy needed to free electrons from the particular surface, and the other term is the kinetic energy of the most energetic ejected electron.
- Photon
- The theoretical particle that carries the force in the electromagnetic field.
- Physical variable
- A mathematical quantity which usually changes its value with time and location; used to describe some physical entity, event, or property.
- Pineal gland
- A small structure situated in the center of the head and connected to the brain that was originally the "third eye," which was located on the top of the head in primitive animals. See also Melatonin.
- Planck's constant
- Fundamental constant of microscopic world denoted by h; h = 6.63 X 10-34 joule-sec.
- Plane wave
- A straight wave; a sinusoidal wave such that the line of crests forms a straight line.
- Plum pudding model
- An early model of the atom according to which electrons are embedded in a positively charged fluid.
- Polarization
- A property of transverse waves such that the wave oscillations can all occur in one direction.
- Position vector
- A vector directed from the origin of coordinates to the position of an object in space.
- Postulate
- Another term for axiom.
- Potential difference
- Usually electric potential; energy per unit charge needed to move a positive charge from one point to another.
- Potential energy
- The work we must do to move an object undergoing an interaction from the reference point to a definite point in space.
- Power (W, kW)
- This is the time rate of doing work, or P = W/T. The practical unit in the metric system is the joule per second, equal to 1 watt. In the English system the unit is foot-pounds per second. For a larger unit, 550 ft. lb/s equal 1 hp. In the electrical context, power in watts, P = IV = I2R, where I is current in amps, V is voltage in volts, and R is resistance in ohms.
- Power density, average (temporal)
- The instantaneous power density integrated over a source repetition period.
- Power density (S)
- Power per unit area normal to the direction of propagation, usually expressed in units of watts per square meter (W/m2) or, for convenience, units such as milliwatts per square centimeter (mW/cm2) or microwatts per square centimeter (µW/cm2). For plane waves, power density, electric field strength (E) and magnetic field strength (H) are related by the impedance of free space, i.e., 377 ohms, as discussed in Section 1 of [this bulletin.] [That would be FCC OET Bulletin 65] Although many survey instruments indicate power density units ("far-field equivalent" power density), the actual quantities measured are E or E2 or H or H2.
- Power density, peak
- The maximum instantaneous power density occurring when power is transmitted.
- Power density, plane-wave equivalent or far-field equivalent
- A commonly-used terms associated with any electromagnetic wave, equal in magnitude to the power density of a plane wave having the same electric (B) or magnetic (H) field strength.
- Precession
- Circular motion performed by a spinning object about a fixed line in space which is not its axis of rotation (spin).
- Promoter
- An agent that promotes the growth of malignant tumors.
- Proton-proton chain
- The series of proton reactions responsible for the energy release from the sun or similar stars; one kind of fusion reaction.
- Pseudovector
- A vector which is invariant under reflection.
- Pythagorean theorem
- The mathematical relation relating the three sides, A, B, C, of a right triangle: A2 + B2 = C2, where C is the hypotenuse.
- Quadrant
- One of the four rectangular areas into which a plane is divided by the x- and y-coordinate axes.
- Quantization
- State of occurring in integral multiples of a basic value; usually applied to physical variables.
- Quantum
- The basic value or unit of some quantized variable.
- Quantum state
- The condition of a system as specified by all applicable quantum numbers.
- Radian
- Unit of angular measure equal to 57.3°, the ratio of arc length to the radius of the circle.
- Radiation
- Energy that is propagated through space in waves or particles; some common forms are: x-rays, microwaves, light, and radio waves.
- Radio frequency (RF)
- That portion of the electromagnetic spectrum extending from 500,000 cycles per second (500 kHz) to 500 million cycles per second (500 MHz).
- Radiofrequency (RF) spectrum
- Although the RF spectrum is formally defined in terms of frequency as extending from 0 to 3000 GHz, for purposes of the FCC's exposure guidelines, the frequency range of interest in 300 kHz to 100 GHz.
- Rationalism
- The philosophical position which asserts that all knowledge can be derived from reason, without appeal to experience.
- Reference frame
- General term for an observer or recording instrument that is making measurements of some phenomenon.
- Reflection, law of
- When light bounces off a mirror, the angle of incidence equals the angle of reflection; both angles are measured from a line perpendicular to the mirror surface.
- Reflection symmetry
- When the mirror image of an object is identical to the object itself, we say the object has reflection symmetry.
- Refraction
- The bending of light as it passes from one medium into another; the amount of bending depends on the speeds of light in the two media.
- Relativity of motion
- The general idea that what kind of motion one observes depends on the motion of the observer.
- Re-radiated field
- An electromagnetic field resulting from currents induced in a secondary, predominantly conducting, object by electromagnetic waves incident on that object from one or more primary radiating structures or antennas. Re-radiated fields are sometimes called "reflected" or more correctly "scattered fields." The scattering object is sometimes called a "reradiator" or "secondary radiator".
- Resonance
- In general this refers to a circumstance in which some aspect of a force-sound waves, for example, has a physical characteristic that "matches" a characteristic of a physical structure, such as the mass of a building, in which case the sound waves will produce vibrations in the building. In the case of electromagnetic radiation, resonance implies a "match" between the wavelength of such radiation with the physical size of a structure. When resonance occurs, the power in the force is maximally transferred to the physical structure.
- Resultant
- The vector which is the sum of two or more vectors; that vector which begins at the tail of the first vector and ends at the tip of the final vector in a vector addition problem.
- Retrograde motion
- The looping motion of a planet as seen from the moving earth.
- RF "hot spot"
- A highly localized area of relatively more intense radio-frequency radiation that manifests itself in two principal ways:
- The presence of intense electric or magnetic fields immediately adjacent to conductive objects that are immersed in lower intensity ambient fields (often referred to as re-radiation), and
- Localized areas, not necessarily immediately close to conductive objects, in which there exists a concentration of RF fields caused by reflections and/or narrow beams produced by high-gain radiating antennas or other highly directional sources. In both cases, the fields are characterized by very rapid changes in field strength with distance. RF hot spots are normally associated with very nonuniform exposure of the body (partial body exposure). This is not to be confused with an actual thermal hot spot within the absorbing body.
- RFNIEMR
- Radio Frequency Non-Ionizing ElectroMagnetic Radiation
- RFR
- Radio Frequency Radiation
- Right-hand rule for magnetic field around straight wire
- Grasp wire so that thumb points in the direction of positive charge flow (the current); then the fingers will curl around wire in the same direction as the magnetic field (see Figure 14.34).
- Root-mean-square (rms)
- The effective value, or the value associated with joule heating, of a periodic electromagnetic wave The rms value is obtained by taking the square root of the mean of the squared value of a function.
- Scalar
- A physical variable which can be uniquely specified by giving a magnitude (number) and a unit.
- Scalar product
- The product of two vectors which yields a scalar; denoted by A B if A and B are the vectors multiplied.
- Scale transformation
- A change in the magnitude of a vector which does not alter its direction.
- Scattered radiation
- An electromagnetic field resulting from currents induced in a secondary, conducting or dielectric object by electromagnetic waves incident on that object from one or more primary sources.
- Second law of thermodynamics
- Law that a system naturally tends to go from a state of higher order to one of lower order.
- Semiconduction
- The conduction of electrical current by the movement of electrons or by the absence of electrons (called "holes") through a crystal lattice. It is the third and most recently discovered method of electrical conduction. The other methods are metallic conduction, which works by means of electrons traveling along a wire, and ionic conduction, which works by movement of charged atoms (ions) in a solution. Semiconductors conduct less current than metals but are far more versatile than either of the other types of conduction. Thus they are the basic materials of the transistors and integrated circuits used in most electronic devices today.
- Shell
- Term applied to a set of energy levels in atoms which are closely spaced to one another but rather widely separated from other sets of levels; denoted by K, L, M, N, etc.
- Short-term exposure
- Exposure for durations less than the corresponding averaging time.
- Simple harmonic motion
- The type of oscillatory motion performed by the projection onto a straight line of a particle moving around a circle with constant speed.
- Sine
- The ratio of the side opposite the angle to the hypotenuse of the right triangle which contains the angle; abbreviated sin.
- Sinusoidal wave
- A simple waveform given by the general graphical shape of the sine function.
- Slope
- (of a vector) The ratio of the magnitude of the y-component to the magnitude of the x-component; also the tangent function.
- Solenoid
- A cylinder around which a (possibly) current-carrying wire has been wound; sometimes referred to as a coil.
- Specific absorption rate (SAR)
- A measure of the rate of energy absorbed by (dissipated in) an incremental mass contained in a volume element of dielectric materials such as biological tissues. SAR is usually expressed in terms of watts per kilogram (W/kg) or milliwatts per gram (mW/g). Guidelines for human exposure to RF fields are based on SAR thresholds where adverse biological effects may occur. When the human body is exposed to an RF field, the SAR experienced is proportional to the squared value of the electric field strength induced in the body.
- Spectrum
- A way to organize a mass of information according to some shared characteristic-for example, a spectrum of neurological diseases. See also Electromagnetic spectrum. The general range of values possible for something and usually arranged along a line; as the spectrum of light or the energy-level spectrum of hydrogen.
- Speed
- The scalar part of velocity.
- Standing waves
- The wave patterns characterized by fixed numbers of loops as occur when a taut rope is oscillated; due to the interference of waves moving back and forth along the rope.
- Static model
- A model of the universe which assumes that the galactic red-shift is not due to an expansion of the universe but, rather, to dust between the galaxies.
- Steady-state model
- A model of the expanding universe which assumes that the expansion of the universe is due to the spontaneous creation of matter throughout the universe.
- Strong interaction
- That interaction responsible for the force holding nucleons together in nuclei and for certain kinds of elementary particle interactions.
- Superposition principle
- If we denote the parts of a wave above the reference line as positive and the parts below as negative, we can add together many waves to produce one resultant wave.
- Synthetic statement
- A statement which says something about the physical world.
- Telecommunications Act of 1996
- Broad sweeping, pro-industry legislation; much of which is now having to be revisited, and amended. Prohibits communities from establishing bans on cellular towers, or from considering biological effects in siting. More information.
- Temperature Scales
- The Celsius scale, formerly known as the centigrade scale, invented by A. Celsius, has 100 divisions between 0° for the freezing point of water and 100° for the boiling point. The Fahrenheit scale, invented by G. D. Fahrenheit, is still used for weather observations and general purposes. On this scale, the freezing point is 32° while the boiling point is 212°, with 180 divisions between. To convert from one scale to the other - TC = 5(TF-32°)/9, and TF = (9TC/5) + 32° The Kelvin or absolute temperature scale was devised by Lord Kelvin. On this scale, the zero point is absolute zero, 273° below 0°C. At 0 K, any material loses all its thermal energy. The divisions of the °C scale and the K scale are the same. (Note: The SI unit for temperature is K for Kelvin, without the degree symbol.) To convert from °C to K, just add 273°. Thus, 0°C equals 273 K. To convert from K to °C, subtract 273°. Then 0 K equals -273°C. Average room temperature is generally considered about 20 to 25°C. This equals 68 to 77°F. On the absolute scale, the corresponding temperatures are 293 to 298 K.
- Tesla (T, µT)
- The Tesla is the MKS unit for measuring magnetic fields. 1 T = 1 Weber/m2. 1 µT = 10 mG. (See also Gauss, Weber/m2).
- Theorem
- A consequence of a theory or mathematical system which is sufficiently useful to warrant special notice.
- Time rate of change
- The change in some physical variable divided by the time interval over which the change occurs.
- Time varying
- Changing with time, such as a time-varying electromagnetic field in which the rate of change is called the frequency and is ex-pressed as the number of oscillations per unit of time.
- Torque
- The vector quantity r x ma where a is the acceleration and r is the displacement of the object from the source of the interaction; denoted T.
- Translation
- A displacement of all points of a figure or body by the same amount in the same direction.
- Transmission line
- A power line carrying high-voltage electricity between regions. Most transmission lines are built on steel towers and operate at voltages between 60 and 765 kV, (60,000 to 765,000 Volts.)
- Transverse wave
- A wave in which the oscillations are perpendicular to the direction of motion of the wave; like an electromagnetic wave. (See Electrmagnetic wave).
- Trough
- The low point on a sinusoidal wave.
- Two-slit interference
- The effect produced when waves pass through two narrow slits; characterized by alternating regions of no waves and intense wave concentration on a distant screen or receiver.
- Uncertainty principle
- Statement that conjugate variables cannot be measured simultaneously with absolute precision.
- Uniform
- Unchanging, constant.
- Unit vector
- A vector with a magnitude of 1.
- Vector
- Any physical variable which can be uniquely specified in terms of a scalar and a direction.
- Vector component
- One of two perpendicular vectors which have a resultant equal to the vector itself; in three dimensions, one of three perpendicular vectors.
- Vector product
- The product of two vectors which yield another vector; denoted by A x B if A and B are the vectors multiplied; direction given by a right-hand rule.
- Velocity
- The displacement of an object divided by the time interval over which the displacement occurs; the time rate of change of position.
- Very low frequency (VLF)
- That portion of the electromagnetic spectrum extending from 1000 cycles per second (1 kHz) to 500,000 cycles per second (500 kHz).
- Volt
- The unit of potential difference; joules per coulomb. Electrical "pressure."
- Volts per meter (V/m)
- Electric fields are measured in Volts per meter, or near power transmission lines, in kV/m.
- Watt
- The unit of measure for electrical power. 1 watt = 1 joule per second. (See Power.)
- Wavelength
- The distance between two consecutive points on a sinusoidal wave that are in phase; measured in meters.
- Weak interaction
- An interaction between elementary particles which violates parity conservation and is responsible for the decay of certain elementary particles.
- Weber/m2 (Wb/m2, µWb)
- Unit for measuring the strength of a magnetic field B. 1 Wb/m2 = 1 Tesla, (T). Frequently expressed in µTeslas, (µT). (See also Tesla, Gauss.)
The material for this glossary came from numerous sources, but started with material from an old physics textbook: Physics: A Modern Perspective", ©;1975 Houghton Mifflin; and some other sources: Cross Currents: the Perils of Electropollution, the Promise of Electromedicine, Dr. Robert O Becker, ©;1990 Dr. Robert O Becker; Basic Electronics, 4th ed. Grob, ©;1977 McGraw Hill, Inc.; Warning: The Electricity Around You May Be Hazardous to Your Health, Ellen Sugarman, ©;1992 Ellen Sugarman. Further entries came from the FCC Office of Engineering and Technology Bulletin 65 which credits the following for their glossary: the American National Standards Institute (ANSI) 1992 RF exposure standard, from NCRP Report No.67, and from the FCC's Rules (47 CFR § 2.1 and § l.131Q).
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