Waves:

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Chapter Seventeen/Eighteen
Waves Sound, Electromagnetic Spectrum, Light
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Wave - a disturbance that transmits energy
through matter or space
- waves transfer energy which often spreads out
as a wave travels (tsunami, ripples, sound)
Vibrations and Waves
- most waves are caused by or related to
vibrating objects
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Medium - the matter through which a wave
travels
Mechanical Waves - a wave that requires a medium
through which to travel (almost all waves are
this type)
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Transverse Waves - a wave that causes the
particles of a medium to vibrate perpendicularly
to the direction the wave travels (p. 501)
Crest - the highest point of a transverse
wave
Trough - the lowest point of a transverse wave
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Longitudinal Waves - a wave that causes the
particles of a medium to vibrate parallel to the
direction the wave travels (p. 502)
Compression - area where the part- icles in a
medium are close together
Rarefaction - area where the part- icles in a
medium are spread out
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Surface Waves - a wave that travels along a
surface separating two media (motion is like that
of a transverse wave, p. 503)
- near a shoreline the wave topples over on
itself because friction with the shore slows down
the bottom of the wave
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Period - the time required for one full
wavelength of a wave to pass a certain point
Frequency - the number of full wavelengths that
pass a point in given time interval
- how rapidly do vibrations occur in a medium
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Wavelength - the distance between a point on a
wave and the same point on the next cycle of the
wave
Amplitude - the maximum displacement of a medium
from the rest position
- the more energy a wave has, the greater its
amplitude
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Behavior of Waves
Reflection - occurs when a wave bounces off a
surface it cannot get through (p. 508)
Refraction - the bending of a wave as it enters a
new medium at an angle (p. 509)

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Diffraction - the bending of a wave as it moves
around an obstacle or passes through a narrow
opening (p. 510)
Interference - when two or more wave combine or
overlap
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Constructive Interference - when two or more
waves combine to produce a wave of larger
displacement (p. 511)
Destructive Interference - when two or more waves
combine to produce a wave of smaller displacement
(p. 511)
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Sound and Hearing
Sound Waves - longitudinal waves travel thru a
medium
Decibel - a unit that compares the intensity of
different sounds
SONAR - SOund Navigation And Ranging determines
distances
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Pitch - the frequency of a sound as we perceive it
Doppler Effect - a change in sound frequency
caused by the motion of the source, or listener,
or both (p.516)
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Electromagnetic Waves - a wave caused by a
disturbance in electric and magnetic fields
and that does not require a medium, also
called light wave (not all light is
visible)
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Electromagnetic Spectrum - the full range of
frequencies that include radio waves, microwaves,
infrared rays, visible light, ultraviolet rays,
X-rays, and gamma rays (left to right, low to
high freq.)
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Radio Waves - used in radio and TV technology
Microwaves - actually short radio waves used to
cook food and cell phone use
Radar - radio detection and ranging (like SONAR)
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Infrared Rays - heat rays (night vision - p.
543 )
Visible light - light humans see (different
colors different wavelengths) (know
ROYGBIV)
Ultraviolet - used in health, medicine, and
agriculture
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- excessive exposure causes sunburn,
wrinkles, skin cancer and damage to the eyes
X-Rays - medicine, industry, and transportation
to make pics of the inside of solid objects
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Gamma Rays - used to kill cancer cells, make pics
of the brain (p.545) and as an inspection tool in
industry
- human exposure to tiny amounts is tolerable,
but overexposure is bad and can be deadly
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Behavior of Light
Transparent - allows most of the light that
strikes it to pass through
Translucent - scatters light (one can see through
it, but objects are not clear such as frosted
glass)
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Opaque - either absorbs or reflects all of the
light that strikes it
Colors
Dispersion - the process in which white light
separates into colors
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- see page 552
- we see what light frequency is REFLECTED BACK
TO US
- white light from the sun contains light from
all visible wavelengths
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Additive Primary Colors (light)
- red, green, blue add to produce yellow, cyan,
magenta or white
Pigment - a material that absorbs some colors,
and reflects others (primary colors are cyan,
yellow, magenta)