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Chapter Seventeen/Eighteen Waves: Sound, Electromagnetic Spectrum, & Light - waves transfer energy which often spreads out as a wave travels (tsunami, ripples, sound ... – PowerPoint PPT presentation

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Title: Waves:


1
Chapter Seventeen/Eighteen
Waves Sound, Electromagnetic Spectrum, Light
2
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
3
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)
4
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
5
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
6
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
7
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
8
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
9
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)

10
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
11
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)
12
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
13
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)
14
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)
15
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.)
16
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)
17
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
18
- 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
19
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
20
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)
21
Opaque - either absorbs or reflects all of the
light that strikes it
Colors
Dispersion - the process in which white light
separates into colors
22
- see page 552
- we see what light frequency is REFLECTED BACK
TO US
- white light from the sun contains light from
all visible wavelengths
23
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)
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