Chapter 13 Review
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 to
Maxwell’s equations
set of four equations that comprise a complete, overarching theory of electromagnetism
microwaves
electromagnetic waves with wavelengths in the range from to ; 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 to ; 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 down to about
visible light
narrow segment of the electromagnetic spectrum to which the normal human eye responds, from about to
X-ray
invisible, penetrating form of very high frequency electromagnetic radiation, overlapping both the ultraviolet range and the -ray range
Key Equations
| Displacement current | |
| Gauss’s law | |
| Gauss’s law for magnetism | |
| Faraday’s law | |
| Ampère-Maxwell law | |
| Wave equation for plane EM wave | |
| Speed of EM waves | |
| Ratio of field to field in electromagnetic wave | |
| Energy flux (Poynting) vector | |
| Average intensity of an electromagnetic wave | |
| Radiation pressure |
Summary
13.1 Maxwell’s Equations and Electromagnetic Waves
- Maxwell’s prediction of electromagnetic waves resulted from his formulation of a complete and symmetric theory of electricity and magnetism, known as Maxwell’s equations.
- The four Maxwell’s equations together with the Lorentz force law encompass the major laws of electricity and magnetism. The first of these is Gauss’s law for electricity; the sec