A
vibration that repeats regularly in space
and time
 Transmitted from one place to another w/out
actually transporting matter
 A transmission of Energy
 Require a medium (substance to travel
through)
 Ex.
Water waves, sound, wave in
string/spring
 Wavelength
– (λ) – distance between
identical parts of a wave. Length of wave
 Amplitude (A)– height of a wave
 Period (T) - time for one full wave to pass
 Frequency (f) – cycles per second … how
many full waves pass by per second
 Frequency
 Period
= 1/ Period
= 1 / Frequency
 Reciprocals


of each other….
Waves per time (frequency)
Time per wave (Period)
 Any




regularly repeating vibration
Pendulum
Spring
Vibrations caused in buildings by wind
Steps of a person walking
 Rules
for waves can be used for anything that
fits in this category
 Transfers
energy not matter
 If stone dropped in water, the disturbance
moves not the water
 Wave
speed depends on the medium
 The more rigid the medium the faster sound
will travel through it
 Wave speed = frequency X wavelength
v
=fλ
 Medium
vibrates in a directions
perpendicular to the direction of the wave
 Medium
vibrates in the same direction that
the wave moves

Constructive Interference


Waves can interfere w/ each other so
that they add together to produce a
larger wave
Destructive Interference


Waves can interfere w/ each other so
that they subtract each other and
cancel out
Demos
• Out of phase
– Destructive interference
• In phase
– Constructive interference
When waves collide w/ a barrier they have a
tendency to wrap around the barrier
 Break walls at the beach
 This is why we can hear a person talking even if
they are around the corner

 Tsunamis
are large waves generated by a
large earthquake or massive landslide
 Travel at hundreds of miles per hour, have
low amplitudes out at sea, but can become
very high when approaching shore
 http://www.funkybiology.com/Destructive_F
orce_of_Tsunami_Waves_mov.mov
 http://www.youtube.com/watch?v=dJBS94G
Vyuo
 http://www.youtube.com/watch?v=BAuWa77
vYDU
 http://www.youtube.com/watch?v=zt5qe_VSEA
 http://www.youtube.com/watch?v=wHtvAlIksU
 http://www.youtube.com/watch?v=sBkMLYU
yUZg&safe=active (new)
 Longitudinal
wave
 Sound travels as a region of compressed air
 The areas in between compressed regions are
called “rarefactions”
 Speed of sound is about 340 m/s in air
 Like any wave the speed depends on the
medium
 Frequency
of a sound wave affects the
“pitch” or how we hear a sound
 Higher frequency, higher the pitch
 Humans can typically hear pitches ranging
from 20 Hz (infrasonic) to 20,000 Hz
(ultrasonic), but that range diminishes as
you age… typically at the high end
 Loudness of a sound is affected only by
amplitude
 http://www.cbu.edu/~jvarrian/applets/dopp
ler1/doppler.htm
 http://www.youtube.com/watch?v=AXhRmv1
mrs4&safe=active

Hearing test
 http://en.wikipedia.org/wiki/52-
Hertz_whale

lonely whale
 http://www.youtube.com/watch?v=h5l4Rt4O
l7M&safe=active

Hearing test
 Waves
From an object that is approaching
have short wavelength, which means they
have a higher freq. And a higher pitch
 waves coming from an object that is moving
away from you have a longer wavelength and
therefore a lower freq, and lower pitch
 Cars approaching and leaving
 Sometimes
the source of a wave can travel
faster than the waves it is creating
 http://www.youtube.com/watch?v=6o0zmaf
xTmE&safe=active
 Can be easily seen with a speed boat
 http://www.youtube.com/watch?v=2Sv4o4Kk
tm4&safe=active
 Sonic boom created when a object or plane
breaks through the sound barrier
•
Standing waves
Stationary wave caused by interference between a wave and its reflection
–
•
Nodes – stationary points
–
•
Where waves our “out of phase”
--- crest lined up with trough
Antinodes- points of largest amplitude
–
•
•
•
•
•
Two waves of equal amplitude and wavelength pass through each other in opposite directions.
Where waves are “in phase”
- crest lined up with crest
Standing Wave in Water
Standing wave demo
Standing waves created by speaker
Swimming pool
When an object is forced into vibrating at one of its natural frequencies, it vibrates in a
manner such that a standing wave is formed within the object.
Tacoma Narrows Bridge
• http://www.youtube.com/watch?v=3mclp9Q
mCGs
Resonance
• When an object vibrates at its natural
frequency, a dramatic increase in amplitude
occurs
• Resonance happens when a standing wave is
created
• Break Glass w/ voice?
• Mythbusters
Beats
• Two tones of slightly different frequency are
sounded together. This produces a fluctuation in
the loudness of combined sounds.
– adfs
• Amount of beats per second is equal to the
difference in frequencies.
– Two tuning forks…. One 340 Hz another 310 Hz are
sounded together. Beats will occur at a frequency of
30 Hz