Waves and Vibrations
Cool Kids Video
Let Us Entertain You!
1
What do you know about
waves?
p85
Write down 5 things that you know about
waves in your notebook. Be specific and
write complete sentences!
Now write 3 questions that you have
about waves
Share out
2
Waves are everywhere in nature
Sound waves,
visible light
waves,
radio waves,
microwaves,
water waves,
sine waves,
telephone chord
waves,
stadium waves,
earthquake
waves,
waves on a
string,
slinky waves
3
Big idea – a method of communication is a means by
which information or ideas can be transferred from your mind to
someone else’s (information like how to build a doghouse)
Fill in the chart with the following methods of
communication and give evidence for your
placement: speaking/listening, writing/reading,
television, morse code, braille, texting, email
Methods of communication that
involve waves
Methods of communication that DO
NOT involve waves
How are each of the 5 senses activated by wave
4
stimuli?
p85
Bell Jar
p85
In Space No One Can Hear You Scream…
Describe the apparatus
Describe what happens to the noise when
the vacuum pump is turned on.
Describe what happens as air reenters
the bell jar.
What conclusion can be drawn about the
slogan for Alien based on what we
observed here?
5
See Sounds
p85
Make some noise!
Record what you notice about the wave
forms
The up/down direction is Amplitude.
Describe when the amplitude gets bigger
or smaller.
The left/right direction is wave length.
Describe how to make the wavelength
change.
6
Rank the sounds
from highest (pitch)
frequency to lowest…
from loudest to
quietest…
What does high
frequency look like?
What does LOUD
look like?
p86
7
Correct
order
8
Investigation #1 (p484-486)
What is the effect of string length and
tension on pitch?
Record your observations and answer lab
questions (steps 1-6) in your notebook
9
Get a stamp when you are done
P87
Wave model physics
DQ: What properties do all sound waves exhibit?
p88
1.) The pitch of a sound corresponds to the
frequency of vibration of the object
producing the sound. The higher the pitch,
the higher the frequency.
2.) Decreasing the length of a vibrating
string increases the pitch (frequency).
3.) Increasing the tension on the string also
increases the pitch (frequency)
10
Finish Invest #1 – Sounds in Vibrating
Strings
Get a stamp when finished
P87
READ p486-487 and answer CU (p487)
1-4
P89
Answer PtoGo (p490) 1-7
Get another stamp
11
What is a wave?
p90
a wave is a oscillation that travels
through a medium from one location to
another. There are no sound waves that
can travel through empty space.
a wave is the motion of a disturbance
Transfer of energy (not matter)
Waves have amplitude, wavelength,
frequency, crests and troughs
12
Wave Basics
p90
13
p90
Wave Period is the time it takes 1
wavelength to pass
Wave frequency is how many waves pass
in one time period
14
Amplitude and Wavelength
p90
1.) How does the sound change when the
amplitude is changed?
2.) How does the sound change when the
wavelength is changed?
15
Investigation #2 p492-498
Distinguish between longitudinal
and transverse waves p91
Part A: Stadium wave
Make a stadium wave with your class
A1. Which direction did the wave move?
A2. Which way did you move?
A3. How did the wave move without you
moving in that direction?
A4. What variables can you change in
your class wave (describe at least 3)? 16
How many waves?
p91
Use a slinky to makes waves. How many
different kinds of waves can you make
with a slinky? Draw each kind in your
notebook…
You have only 10 minutes…
17
Part B: Transverse waves and
standing waves
p91
B1. Which direction did the wave move?
B2. Which way did the tape in the middle
of the slinky move?
B3. Describe a transverse wave.
B4. What word best describes a
transverse wave?
18
Part C: Longitudinal waves
p91
C1. Which direction did the wave move?
C2. Which way did the tape in the middle
of the slinky move?
C3. Describe a longitudinal wave.
C4. What word best describes a
longitudinal wave?
C5. What kind of wave is a stadium
wave? Use slinky evidence to support
your answer.
19
Wave vocab
P93
Define each vocabulary word using your
own words (do not copy the book
definition) and draw a picture to show the
meaning of the word
Vibrate pitch amplitude crest/peak
trough wavelength node antinode
periodic wave standing wave wave
medium frequency period
Transverse wave longitudinal wave
20
Finish
p92
Part D: Wave Interference ( wavey sim
worksheet…use phet wave interference
sim)
Read p498-502. Answer Cu (p502) 1-3
Get a stamp when you finish
Vocab Active Physics p498-501. Define
in your own words and draw a picture
p93
21
Directions: ppt slides 22-45
highlight or circle gold words on ppt
watch all animations
click/watch all underlined links
answer any questions
get each page stamped when finished
P94-95
 Your wave model (what do you know
about waves…list at least 5)





Get stamps when finished and finish vocab 22
Slinky Wave
Let’s use a slinky wave as an example.
When the slinky is stretched from end to
end and is held at rest, it assumes a
natural position known as the
equilibrium or rest position.
To introduce a wave here we must first
create a disturbance.
We must move a particle away from its
rest position.
23
Slinky Wave
One way to do this is to push the slinky forward
the beginning of the slinky moves away from its
equilibrium position and then back.
the disturbance continues down the slinky.
this disturbance that moves down the slinky is
called a pulse.
if we keep “pulsing” the slinky back and forth,
we could get a repeating disturbance.
24
Slinky Wave
This disturbance would look something like this
This type of wave is called a LONGITUDINAL wave.
The pulse is transferred through the medium of the
slinky, but the slinky itself does not actually move.
It just displaces from its rest position and then
returns to it.
So what really is being transferred?
25
Slinky Wave
Energy is being transferred.
The metal of the slinky is the MEDIUM in that
transfers the energy pulse of the wave.
The medium ends up in the same place as it
started … it just gets disturbed and then returns
to it rest position.
The same thing can be seen with a stadium
wave (think back to the stadium wave we made
in class).
26
Longitudinal Wave
The wave we see here is a longitudinal wave.
The medium particles vibrate parallel to the
motion of the pulse.
This is the same type of wave that we use to
transfer sound.
How is sound made in your vocal cords and
how does it gets to your ears?

show tuning fork demo
27
Transverse waves
A second type of wave is a transverse
wave.
We said in a longitudinal wave the pulse
travels in a direction parallel to the
disturbance.
In a transverse wave the pulse travels
perpendicular to the disturbance.
28
Transverse Waves
The differences between the two can be
seen. List 2 differences…
29
Transverse Waves
Transverse waves occur when we wiggle
the slinky back and forth.
They also occur when the source
disturbance follows a periodic motion.
A spring or a pendulum can accomplish
this.
The wave formed here is a SINE wave.
 http://webphysics.davidson.edu/course_material/py130/demo/illustration1
6_2.html
30
Swings and Springs
Describe 1 cycle of a
pendulum swing
Describe 1 cycle of a
spring “bounce”
31
Anatomy of a Wave
Now we can begin to describe the
anatomy of our waves.
We will use a transverse wave to describe
this since it is easier to see the pieces.
32
Anatomy of a Wave
In our wave here the dashed line represents the
equilibrium position.
Once the medium is disturbed, it moves away
from this position and then returns to it
33
Anatomy of a Wave
crest
The points A and F are called the CRESTS
of the wave.
This is the point where the wave exhibits the
maximum amount of positive or upwards
displacement
34
Anatomy of a Wave
trough
The points D and I are called the
TROUGHS of the wave.
These are the points where the wave
exhibits its maximum negative or downward
displacement.
35
Anatomy of a Wave
Amplitude
The distance between the dashed line and
point A is called the Amplitude of the wave.\
This is the maximum displacement that the
wave moves away from its equilibrium.
36
Anatomy of a Wave
wavelength
The distance between two consecutive similar
points (in this case two crests) is called the
wavelength.
This is the length of the wave pulse.
Between what other points is can a wavelength be
measured?
37
Anatomy of a Wave
What else can we determine?
We know that things that repeat have a
frequency and a period. How could we find
a frequency and a period of a wave? What
needs to be measured?
38
Wave frequency
We know that frequency measure how
often something happens over a certain
amount of time.
We can measure how many times a pulse
passes a fixed point over a given amount
of time, and this will give us the
frequency.
39
Wave frequency
frequency measures how often something happens over a
certain amount of time
Suppose I wiggle a slinky back and forth,
and count that 6 waves pass a point in 2
seconds. What would the frequency be?
6 waves/2 seconds = 3 cycles / second
3 Hz
we use the term Hertz (Hz) to stand for
cycles per second.
40
Wave Period
The period describes the same thing as it
did with a pendulum.
It is the time it takes for one cycle to
complete.
It also is the reciprocal of the frequency.
T = 1 / f
f = 1 / T
let’s see if you get it.
41
Wave Speed
We can use what we know to determine
how fast a wave is moving.
What is the formula for velocity?
velocity = distance / time
What distance do we know about a wave
wavelength
and what time do we know
period
42
Wave Speed
so if we plug these in we get
velocity =
length of pulse /
time for pulse to move pass a fixed point
v =  / T
we will use the symbol  (greek letter
lambda) to represent wavelength
43
Wave Speed
v =  / T
but what does T equal
T = 1 / f
so we can also write
v = f 
velocity = frequency * wavelength
This is known as the wave equation.
examples
44
Wave Equation v=λf
1.) Ocean waves 12 m in length strike a
seawall with a frequency of 0.5 Hz. How
fast do these waves move? v=λf
2.) sound waves traveling at 350 m/s are
made by a tuning fork that vibrates 384
times each second. What is the wavelength
of the sound waves produced? λ=v/f
3.) The light rays from a laser pointer have
a wavelength of 670nm and travel at
300Mm/s. What is the frequency of the
source of these waves? f=v/λ
45
Wave Equation v=λ/T
p95
4.) A nurse counts 76 heartbeats in one
minute. What are the period and frequency
of the hearts’ oscillations?
f=vibrations/time
period=1/f
5.) New York’s 300m tall Citicorp Tower
oscillates in the wind with a period of 6.80
s. Calculate its velocity of vibration.
v=λ/T
What is the frequency of the wave? f=v/λ
46
Wave Equation answers
p95
1.) v=λf = 12/0.5 = 6 m/s
2.) λ=v/f = 350/384 = 0.91 m
3.) f=v/λ = 300/670 =0.45 hz
4.) f=vibrations/time = 76/60 =1.27 hz
period=1/f = 1/1.27 = 0.78 beats/sec
5.) Calculate its velocity of vibration.
v=λ/T = 300/6.80 = 44.23 m/s
What is the frequency of the wave?
f=v/λ = 44.23/300 = 0.14 hz
47
Wave model
p88
4.) Waves are disturbances that travel through
a medium ex: longitudinal sound waves
5.) Only ElectroMagnetic (EM) waves can
travel through a vacuum (empty space). Ex:
transverse light waves.
6.) Period = the time required for 1 cycle
7.) Frequency = cycles/time =1/period f=1/T
8.) Wave equation: wavelength λ=v/f or v =f λ
9.) Waves transfer energy from one place to
another. Large amplitude=large energy 48
P99
49
50
51
Introduction to Waves
p96
1.) The following waves pass in 1 second.
Mark one wavelength on each wave. What
is their period and frequency?
52
More Wave model physics
10. Transverse waves have disturbances
perpendicular to the wave direction. Light
(and all other EM waves) are transverse.
11. Longitudinal waves have the
disturbance in the same direction as the
wave. All sounds are longitudinal (which is
why you lose your hearing from loud
sounds)
12.) standing waves do not move. They are
made of nodes and antinodes.
53
p88
Quiz today!
Turn in your Quiz when finished
Finish Introduction to waves worksheet
Phet: Finding Wave Properties (wave on a
string simulation) NOT TODAY
Turn in your notebook TODAY (because of
the holiday Monday…)
Extra credit available….check the calendar
54
P96-97
Wave Behavior
Now we know all about waves:
How to describe them, measure them and
analyze them.
So let’s begin looking at some wave
behaviors…
55
P100
Free End
One boundary type is when a wave’s
medium is NOT attached to a stationary
object as a free end.
In this situation, the end of the medium is
allowed to slide up and down.
What would happen in this case?
56
Free End Animation
57
Free End
Here the reflected pulse is not inverted.
It is identical to the incident pulse, except
it is moving in the opposite direction.
The speed, wavelength, and amplitude
are the same as the incident pulse.
58
Fixed End
One type of boundary that a wave may
encounter is that it may be attached to a
fixed end.
In this case, the end of the medium will
not be able to move.
What is going to happen if a wave pulse
goes down this string and encounters the
fixed end?
59
Fixed End Animation
60
Fixed End
Here the incident pulse is an upward
pulse.
The reflected pulse is upside-down. It is
inverted.
The reflected pulse has the same speed,
wavelength, and amplitude as the
incident pulse.
61
Change in Medium
Our third boundary condition is when the
medium of a wave changes.
Think of a thin rope attached to a thin
rope. The point where the two ropes are
attached is the boundary.
At this point, a wave pulse will transfer
from one medium to another.
What will happen here?
62
Change in Medium Animation
Test your understanding
63
Change in Medium
In this situation part of the wave is reflected,
and part of the wave is transmitted.
Part of the wave energy is transferred to the
more dense medium, and part is reflected.
The transmitted pulse is upright, while the
reflected pulse is inverted.
64
Change in Medium
The speed and wavelength of the reflected
wave remain the same, but the amplitude
decreases.
The speed, wavelength, and amplitude of
the transmitted pulse are all smaller than
in the incident pulse.
65
Wave Interaction
All we have left to discover is how waves
interact with each other.
When two waves meet while traveling
along the same medium it is called
INTERFERENCE.
66
Constructive Interference
Let’s consider two waves moving towards
each other, both having a positive
upward amplitude.
What will happen when they meet?
67
Constructive Interference
They will ADD together to produce a
greater amplitude.
This is known as CONSTRUCTIVE
INTERFERENCE.
68
Destructive Interference
Now let’s consider the opposite, two
waves moving towards each other, one
having a positive (upward) and one a
negative (downward) amplitude.
What will happen when they meet?
69
Destructive Interference
P100
This time when they add together they
will produce a smaller amplitude.
This is know as DESTRUCTIVE
INTERFERENCE.
70
P102
71
P101
Bouncing Pulses
Finish both sides
Get a stamp
72
73
74
75
Check Your Understanding
p85
P101
 Which points will produce constructive interference and
which will produce destructive interference?
 Constructive
G, J, M, N
 Destructive
H, I, K, L, O
76
Standing waves
Standing waves
appear to be
stationary
(standing still)
and the wave
appears not to
move. This is the
result of wave
interference
between two
waves.
P101
77
Resonance
P102
Resonance is a phenomena when the
frequency of forced vibrations matches the
objects natural frequency and this causes a
dramatic increase in amplitude.
 Break a glass
 Watch the amazing "Gallopin' Gertie" November 7,
1940 film clip. Slender, elegant and graceful, the
Tacoma Narrows Bridge stretched like a steel ribbon
across Puget Sound in 1940. The third longest
suspension span in the world opened on July 1st. Only
four months later, the great span's short life ended in
disaster. Break a bridge
78
Examples of wave behavior
Speaker waves
Speaker waves with corn starch
More speaker waves with corn starch
Active noise control
Beat (acoustics)
Diffraction
Double-slit experiment
Thin film interference
79
P102
80
P102
Finish and get a stamp
81
But how do they interact?
Write a description and draw a
picture for each behavior.
A. Free end
B. Fixed end
C. Change in medium
D. Constructive Interference
E. Destructive Interference
F. Standing waves
G. Resonance
P99-100
82
3-2-1
P99-100
Complete the following for your assigned
wave behavior. We will share out to the
class in 10 minutes. Use a whiteboard
3 new things that you learned (definition,
picture, example)
2 new questions about waves
1 connection to a previous activity
Record each wave behavior in your
notebook as presented
83
Moving sources
p103
What happens to sounds from a stationary
source?
What happens to sound
when a Stationary source
begins moving?
What happens to sound as the source
moves faster?
84
Doppler effect
p103
Describe the Doppler Effect
85
Moving sources
Boat wakes
Doppler effect
Doppler effect 2
Doppler effect 3
Doppler at speed of sound
Doppler at supersonic speeds
Sonic boom
***The Doppler Effect
86
P104
87
P104
88
P104
89
Waves review
Quiz corrections
Ch 26 cornell notes 10 points extra credit
Extra credit due Monday 1/26
Finish CDP 25-1 and CDP 25-2
Finish PtoGo (p505-507) 1-6 today
Get your work stamped before you go
P105
90
Investigation #3 (p508-510)
Sounds in Strings Revisited
P106
Draw the standing waves produced by the wave machines.
Label wavelength(s), nodes, internodes
Go to the lab
Length of string
X2=wavelength
pitch
bench to fill in the
chart
1.) What happens to the wavelength as you change the
length of the string?
2.) What happens to the pitch (frequency)?
3.) What wave property changes to make the frequency
higher? (hint: v =f λ and wave speed does not change!)
Finish PtoGo (p505-507) 1-12 Get a stamp91
Flame Organ
p107
Describe the apparatus/draw a picture
Record your observations (at least 3)
Apply a sound concept/principle/vocab
word to this phenomena. Define the
vocab word(s) and explain how the flame
organ demonstrates this.
A different view
92
Wave model
p88
13.) The pitch of a sound corresponds to the
frequency of vibration of the object producing the
sound. The higher the pitch, the higher the
frequency.
14.) Decreasing the length of a vibrating string
increases the frequency (pitch).
15.) Increasing the tension on the string increases
the frequency also
16.) Wave velocity=frequency *wavelength
17.) When the length of a vibrating string is
decreased, the speed remains the same, so the
frequency must increase (higher pitch sound)
93
P107-8
Finish…
Do CDP 26-1
READ p511-513 and answer CU (p514)
1-4
Answer PtoGo (p517) 1-7
Get a stamp when finished
Quiz Friday!
94
New project!
Let Us Entertain You!
p109
Read Active Physics p480-481 and then
look at the rest of the unit (p482-588)
Watch the youtube clips Warm Wishes Campbell’s
soup Blue Man Group 1 Blueman drumbone and wine glasses,
Veggie orchestra, RC Car, project example 1, project example 2
In your notebook record
3 project ideas
3 questions about the project
3 sound principles that you
might include
3 light special effects that
you would like to use
95
Project plans
Count off 1-4
Make groups containing someone
representing each number 1-4
Share what you wrote on page 106 with
your partners
Each partner will record something on
one of the whiteboards
If you have something to add to another
whiteboard, you may
Light idea
96
Build your own musical
instrument tutorials
Build your own string instrument
Build your own percussion
Build your own woodwind
Build your own brass
97
Benchmark #1: Build your own
instrument
p110
Watch each tutorial (4 total)
Build your own string instrument…
Draw and label a picture of one
instrument from EACH tutorial
List the materials that are used
Explain how each instrument makes at
least 5 different notes (pitches)
Summary: which instrument are you
going to make? Explain your steps…
98
p111
Portfolio entry #1- Pitch
Write what you KNOW about pitch
99
Portfolio entry #1- Pitch
p111
Write what you KNOW about pitch
Read about pitch (Active Physics page 486-487)
Add to your written response…In YOUR OWN WORDS!
Did you use many physics words (frequency, transverse wave, wave length)?
Use your RUBRIC. Do you have
• Definition
• Relationship (what happens to the pitch when frequency changes?)
• Musical instrument example
• Great detail
• Picture or diagram (label pictures of high and low pitch)
Share out with a partner…partner, what score would you give this response? How can
it be made better?
Edit your response until it becomes a perfect 4!
Woodwind instruments
Examples: pan flute, recorder
Vibration made by forcing air across a
thin edge
Pitch changed when you use your fingers
to plug holes in the length of the
instrument (thus changing the length of
the tube)
101
String instruments
Examples: guitar, violin, harp
Vibration made by plucking the strings
(or drawing a bow across the strings)
Pitch can be changed by either adjusting
the tension in the strings, or changing the
length of the strings
102
Percussion instruments
Examples: bottle/glasses filled with
water, pipes/tubes/wood pieces of various
lengths (xylophone), drums (made from
cardboard tubes)
Vibration made by gently striking surface
Pitch changed by having various lengths
of substance (water, wood, cardboard)
103
Brass instruments
Examples: trombone, flute, brass horn
Vibrations made by forcing air through
your lips
Pitch changed by changing the length of
the tube
104
4 season partners
Spring-
Fall-
Winter-
Summer-
105