Term	Definition
Amplitude	Maximum displacement of a wave from its rest position; directly related to the wave's energy.
Antenna	A device that converts electrical signals into electromagnetic waves (transmitting) or electromagnetic waves into electrical signals (receiving).
Carrier wave	A constant-frequency wave used to carry information by means of modulation.
Coherence	The property of waves being in phase with each other, producing a stable interference pattern. Lasers produce highly coherent light.
Diffraction	The bending and spreading of waves when they encounter obstacles or pass through narrow openings.
Doppler effect	The change in observed frequency when a wave source and observer are moving relative to each other.
EM spectrum	The complete range of electromagnetic radiation, ordered by frequency from radio waves to gamma rays.
Frequency	The number of complete wave cycles passing a point per second, measured in Hertz (Hz).
Hertz (Hz)	The SI unit of frequency — one cycle per second. Named after Heinrich Hertz, who first demonstrated radio waves.
Interference	The phenomenon that occurs when two waves overlap, producing regions of reinforcement (constructive) or cancellation (destructive).
Ionizing radiation	Electromagnetic radiation with enough energy per photon to remove electrons from atoms (X-rays and gamma rays).
Magnetron	A vacuum tube that generates microwaves; the core component of microwave ovens and early radar systems.
Modulation	The process of encoding information onto a carrier wave by varying its amplitude (AM), frequency (FM), or phase (PM).
Photon	A single quantum (particle) of electromagnetic radiation. The energy of a photon is \(E = hf\).
Polarization	The orientation of the electric field oscillation in an electromagnetic wave.
Refraction	The bending of waves when they pass from one medium into another with a different refractive index.
Refractive index	A measure of how much a material slows light relative to vacuum. Water has \(n \approx 1.33\), glass \(n \approx 1.5\), diamond \(n \approx 2.42\).
Resonance	The tendency of a system to oscillate at maximum amplitude at certain natural frequencies. Radio tuning circuits exploit resonance.
Total internal reflection	The complete reflection of light within a medium when it strikes the boundary at an angle shallower than the critical angle. The principle behind fiber optics.
Trilateration	A method of determining position by measuring distances from three or more known reference points. The basis of GPS.
Wavelength	The distance between two consecutive crests (or troughs) of a wave, typically denoted by \(\lambda\).