Memory's Domain
Waves : a few definations by J. Hazlett
Wave: A disturbance that moves without carrying the stuff it disturbs along with it.
There are two kinds, mechanical (which requires a medium) and electromagnetic (which
does not). Not to be confused with a greeting involving hand motion.
Transverse wave: A wave in which the affected particles move side to side
(perpendicular to wave motion), like a water wave.
Longitudinal Wave: A wave in which the effected particles move back and forth
(parallel to wave motion), like sound.
Crest: Highest point on a wave.
Trough: Lowest point on a wave.
Wavelength: Distance between two crests, two troughs, or more generally any
two identical points on two different waves. Measured in meters and represented by
lambda, l.
Amplitude: Maximum distance of wave from equilibrium, i.e. distance from crest
or trough to equilibrium. Measured in meters and represented by the letter A.
Frequency: The number of waves that move through a given point over a given
time. Measured in Hertz (1/s) and represented by the letter f. It is determined exclusively
by the source, and no meddling is gonna change that.
Velocity: How fast the durn thing moves. Just like any other velocity, wave
velocity is measured in m/s and is represented by V. However, wave velocity can be
found by the handy, useful equation V=lf. In a given medium, velocity of a wave is
always the same.
String: A long thin thing. It has several properties. It has both mass and length,
and we represent mass per unit length as mu, m (as if there weren't enough uses for this
poor Greek letter). Velocity of a wave on a string is equal to �(F/m), or the square root of
force (tension) applied to a string divided by mass per unit length.
Superpositioning: Putting one wave on top of another. Similar displacements
(crest-to-crest, for example) add; opposite displacements (crest-to-trough, for example)
subtract. Waves can travel through one another without getting permanently deformed,
just temporarily confused.
Constructive Interference: When waves add. Makes bigger wave.
Destructive interference: When waves subtract. Makes smaller wave, or no wave.
Reflection: Lookin' good in a mirror. Also, the result of a wave attempting to
change mediums. The reflection can be either normal or, if the new medium is more rigid
than the old, inverted (upside down or backwards), like the image in a mirror. Waves
reflect away at the same angle they strike the surface with.
Transmission: Another result of a wave attempting to change mediums. The
delivery of a portion of the wave energy into the new medium. Reflection and
transmission occur anytime a wave changes mediums.
Node: Place where a waves cancel one another out, leaving the medium at the
equilibrium position. Ending wave movement in a string (or presumably anything else) at
a node will not change the behavior of the rest of the wave.
Slinky: Advanced coiled metallic medium used for unprecedented studies in wave
mechanics. Can carry both longitudinal and transverse pulses. Miraculous development in
scientific study leading to incredible new understanding of wave behavior. Or, a machine
spring used as a child's toy. You decide.
� 1997 [email protected]
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