Waves in a Nutshell:
Waves are periodic disturbances that carry energy from one place to another. Waves occur in various forms.
Longitudinal waves require a medium for propagation. When a longitudinal wave passes, the particles of the medium move back and forth in a parallel (then anti-parallel) direction to the wave as the disturbance continues in its original direction. Sound is the best known longitudinal wave. Air is the medium we most experience sound in but sound occurs in any form of matter.
Transverse waves ordinarily move through a medium as well (the most important exception will be discussed). A transverse wave moves through a medium while the particles of the medium move back and forth perpendicular to the disturbance itself.
One example of a transverse wave is electromagnetic "radiation" that propagates through space (without a medium). Electromagnetic waves can be visualized as two oscillating fields, one magnetic and one electric, that can be depicted as a three dimensional transverse wave.
Some Vocabulary:
Wavelength: The distance from one crest on a train of waves to the next crest. Measured in meters.
Frequency: The number of complete wave cycles to pass one point in a period of time (one second). Measured in Hz (/s or s-1).
Wave speed: The speed at which a particular wave carries a unit of energy (the matter it moves through experiences no net displacement) through a distance. Measured in m/s.
Period: The time required for a particular disturbance to complete one cycle. The reciprocal of frequency. Measured in seconds.
Amplitude: The maximum displacement from the neutral or equilibrium position experienced by a particle of the medium that the wave travels through.
Standing Wave: A wave that forms when the disturbance that creates the wave occurs at the natural frequency of the medium so that the transmitted wave interferes with its own reflection. The resulting wave form can appear to "stand" frozen in space even though energy is moving continually through it.
Node: A point in a standing wave where the maximum displacement from neutral is zero -- the medium appears never to move at this point.
Antinode: The point of a standing wave, halfway between nodes, where the amplitude is a maximum (both positively and negatively).
Crest: The point of a wave with maximum positive displacement from neutral.
Trough: The point of a wave with a maximum negative displacement from neutral.
Transverse Wave: Any wave characterized by a motion of particles of medium that is perpendicular to the motion of the energy carried by the wave (as seen by observing the changing position of a crest or trough).
Longitudinal Wave: Any wave characterized by a motion of particles that is parallel (then antiparallel) to the motion of the energy carried by the wave (as seen by observing the changing position of a compression or rarefaction).
Compression: The crest of a longitudinal wave. A region of the medium through which the wave travels that has a more dense population of particles than its surroundings.
Rarefaction: The trough of a longitudinal wave. A region of the medium through which the wave travels that has a less dense population of particles than its surroundings.
Human Hearing:
