Wave Concepts
and some facts and terms
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Mechanical waves can be thought of as a disturbance
in a medium. This disturbance transfers energy from one place to
another, although the medium itself does not travel.
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There are two basic kinds of waves, transverse
and longitudinal.
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A wave pulse is a single disturbance.
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A traveling wave is produced by repeated
disturbances in some pattern (aka simple harmonic motion).
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Period and frequency of a wave are inversely
related, if one goes up the other must go down.
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Wavelength and frequency of
a wave are inversely related, if one goes up the other must go down.
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Velocity of a wave is its wavelength multiplied
by its frequency.
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A large amplitude wave transfers more
energy than a small amplitude wave, all other things being equal.
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Two waves can be in one place at the same
time (not true for matter). When they are, they add (or subtract)
to produce a "combination wave."
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Constructive interference is the term
for two (or more) waves that add their crests together. Destructive
interference is the term for two (or more) waves that add crests
to troughs, effectively canceling part of the wave.
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In the ideal case, two waves can pass through
each other without undergoing change.
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A wave that passes into a different medium
is partially reflected and partially transmitted.
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A wave that passes from a less dense to a
more dense medium produces an inverted reflected wave. (The opposite
produces an upright reflected wave.)
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A standing wave results when identical
waves travel in opposite directions. A wave on a string is an example.
A standing wave has nodes and antinodes.
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The law of reflection is true for waves.
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Waves refract, or change direction
(bend) when they meet a change in their medium at an angle.
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Waves refract because one part of the wave
slows down before another.
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Waves pass through a small aperture (hole)
in a barrier by spreading out through the hole (diffraction).
Waves can also bend around an obstacle (also diffraction). When diffraction
occurs because of nearby holes, a pattern of alternating constructive and
destructive interference may be set up.
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A wave front can be thought of as infinitely
many miniature wave fronts (Huygens' Principle).
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