Sections
Glossary
Glossary
- amplitude
- the height, or magnitude, of an electromagnetic wave
- amplitude modulation (AM)
- a method for placing information on electromagnetic waves by modulating the amplitude of a carrier wave with an audio signal, resulting in a wave with constant frequency but varying amplitude
- carrier wave
- an electromagnetic wave that carries a signal by modulation of its amplitude or frequency
- electric field
- a vector quantity (E); the lines of electric force per unit charge, moving radially outward from a positive charge and in toward a negative charge
- electric field lines
- a pattern of imaginary lines that extend between an electric source and charged objects in the surrounding area, with arrows pointed away from positively charged objects and toward negatively charged objects. The more lines in the pattern, the stronger the electric field in that region
- electric field strength
- the magnitude of the electric field, denoted E-field
- electromagnetic spectrum
- the full range of wavelengths or frequencies of electromagnetic radiation
- electromagnetic waves
- radiation in the form of waves of electric and magnetic energy
- electromotive force (emf)
- energy produced per unit charge, drawn from a source that produces an electrical current
- extremely low frequency (ELF)
- electromagnetic radiation with wavelengths usually in the range of 0 to 300 Hz, but also about 1kHz
- frequency
- the number of complete wave cycles (up-down-up) passing a given point within one second (cycles/second)
- frequency modulation (FM)
- a method of placing information on electromagnetic waves by modulating the frequency of a carrier wave with an audio signal, producing a wave of constant amplitude but varying frequency
- gamma ray
- ( ray); extremely high frequency electromagnetic radiation emitted by the nucleus of an atom, either from natural nuclear decay or induced nuclear processes in nuclear reactors and weapons. The lower end of the ray frequency range overlaps the upper end of the X-ray range, but rays can have the highest frequency of any electromagnetic radiation
- hertz
- an SI unit denoting the frequency of an electromagnetic wave, in cycles per second
- infrared radiation (IR)
- a region of the electromagnetic spectrum with a frequency range that extends from just below the red region of the visible light spectrum up to the microwave region, or from to
- intensity
- the power of an electric or magnetic field per unit area, for example, Watts per square meter
- magnetic field
- a vector quantity (B); can be used to determine the magnetic force on a moving charged particle
- magnetic field lines
- a pattern of continuous, imaginary lines that emerge from and enter into opposite magnetic poles. The density of the lines indicates the magnitude of the magnetic field
- magnetic field strength
- the magnitude of the magnetic field, denoted B-field
- maximum field strength
- the maximum amplitude an electromagnetic wave can reach, representing the maximum amount of electric force and/or magnetic flux that the wave can exert
- Maxwell’s equations
- a set of four equations that comprise a complete, overarching theory of electromagnetism
- microwaves
- electromagnetic waves with wavelengths in the range from 1 mm to 1 m; they can be produced by currents in macroscopic circuits and devices
- oscillate
- to fluctuate back and forth in a steady beat
- radar
- a common application of microwaves. Radar can determine the distance to objects as diverse as clouds and aircraft, as well as determine the speed of a car or the intensity of a rainstorm
- radio waves
- electromagnetic waves with wavelengths in the range from 1 mm to 100 km; they are produced by currents in wires and circuits and by astronomical phenomena
- resonant
- a system that displays enhanced oscillation when subjected to a periodic disturbance of the same frequency as its natural frequency
- RLC circuit
- an electric circuit that includes a resistor, capacitor and inductor
- speed of light
- in a vacuum, such as space, the speed of light is a constant 3 x 108 m/s
- standing wave
- a wave that oscillates in place, with nodes where no motion happens
- thermal agitation
- the thermal motion of atoms and molecules in any object at a temperature above absolute zero, which causes them to emit and absorb radiation
- transverse wave
- a wave, such as an electromagnetic wave, which oscillates perpendicular to the axis along the line of travel
- TV
- video and audio signals broadcast on electromagnetic waves
- ultra-high frequency (UHF)
- TV channels in an even higher frequency range than VHF, of 470 to 1,000 MHz
- ultraviolet radiation (UV)
- electromagnetic radiation in the range extending upward in frequency from violet light and overlapping with the lowest X-ray frequencies, with wavelengths from 400 nm down to about 10 nm
- very high frequency (VHF)
- TV channels utilizing frequencies in the two ranges of 54 to 88 MHz and 174 to 222 MHz
- visible light
- the narrow segment of the electromagnetic spectrum to which the normal human eye responds
- wavelength
- the distance from one peak to the next in a wave
- X-ray
- invisible, penetrating form of very high frequency electromagnetic radiation, overlapping both the ultraviolet range and the ray range