Key Terms
- displacement current
- extra term in Maxwell’s equations that is analogous to a real current but accounts for a changing electric field producing a magnetic field, even when the real current is present
- 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
- infrared radiation
- 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
- Maxwell’s equations
- 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
- Poynting vector
- vector equal to the cross product of the electric-and magnetic fields, that describes the flow of electromagnetic energy through a surface
- radar
- 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
- radiation pressure
- force divided by area applied by an electromagnetic wave on a surface
- 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
- thermal agitation
- thermal motion of atoms and molecules in any object at a temperature above absolute zero, which causes them to emit and absorb radiation
- ultraviolet radiation
- 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
- visible light
- narrow segment of the electromagnetic spectrum to which the normal human eye responds, from about 400 to 750 nm
- X-ray
- invisible, penetrating form of very high frequency electromagnetic radiation, overlapping both the ultraviolet range and the -ray range