Introduction to Waves
Surf’s up dude!
Objectives
⚫Learn the basic characteristics of waves and use them
to solve simple problems.
What Are Waves?
⚫A wave is a disturbance that carries energy through
matter or space without transferring matter.
⚫Wave Demo
Ocean Waves
Wave Characteristics
⚫Amplitude: The greatest
distance from
equilibrium.
⚫The bigger the amplitude
of the wave, the more
energy the wave has.
Wave Characteristics
⚫Crest: The top point of a wave.
⚫Trough: The bottom point of a wave.
Wave Characteristics
⚫Wavelength: The shortest distance between points
where the wave pattern repeats itself.
Wave Characteristics
⚫Phase: Any two points on a wave that are one or
more whole wavelengths apart are said to be “in
phase”.
Wave Characteristics
⚫Frequency: Is the number of complete oscillations a
point on that wave makes each second.
Wave Characteristics
⚫
Wave Characteristics
⚫
Example
⚫
Checkpoint
⚫
Practice
⚫On page 393 of the textbook answer questions 15, 16,
17, 19, 22, and 24.
Answers
⚫ 15. 343m/s, 2.29x10^-3s, 0.787m
⚫ 16. You should shake it at a lower frequency because
wavelength varies inversely with frequency.
⚫ 17. 2.45m/s
⚫ 19. 2.50m
⚫ 22. The frequency is one-half of its original value.
⚫ 24. The wavelength increases to 1.5 times its original value.
Bellringer
⚫What does a wave
transfer?
⚫Energy, NOT MASS!
DO
STOP
WORK
Objectives
⚫Review and solidify the material you learned and
practiced yesterday.
⚫Learn about the different types of waves.
⚫Study, create, and destroy different wave types.
Practice
⚫On page 393 of the textbook answer questions 15, 16,
17, 19, 22, and 24.
Answers
⚫ 15. 343m/s, 2.29x10^-3s, 0.787m
⚫ 16. You should shake it at a lower frequency because
wavelength varies inversely with frequency.
⚫ 17. 2.45m/s
⚫ 19. 2.50m
⚫ 22. The frequency is one-half of its original value.
⚫ 24. The wavelength increases to 1.5 times its original value.
Art Time – Example Part Two
⚫Draw two more cycles of the red wave.
Art Time – Example Part Two
⚫Draw one more cycles of the blue wave.
Art Time – Example Part Two
⚫What is the wavelength of the red wave?
⚫2.0m
Art Time – Example Part Two
⚫What is the wavelength of the blue wave?
⚫4.0m
Art Time – Example Part Two
⚫What is the amplitude of the red wave?
⚫0.5m
Art Time – Example Part Two
⚫What is the amplitude of the blue wave?
⚫0.25m
Art Time – Example Part Two
⚫If this is a snapshot of how far each wave traveled in 1
second, what is the frequency of the red wave?
⚫3.0Hz
Art Time – Example Part Two
⚫If this is a snapshot of how far each wave traveled in 1
second, what is the frequency of the blue wave?
⚫1.5Hz
Art Time – Example Part Two
⚫Are the red and blue wave in phase with each other?
⚫Nope
Art Time – Example Part Two
⚫Mark two spots on each wave that are in phase with
each other.
You try
⚫ Draw the following waves on the same graph:
1. A wave with an amplitude of 6m and a wavelength of
3m.
2. A wave with an amplitude of 2m and a wavelength of
2m.
3. A wave with an amplitude of 3m and a wavelength of
4m.
⚫ Which wave has the greatest frequency if they’re all
traveling at the same speed?
Types of Waves
⚫There are two types of waves!
1. Transverse Waves: A wave that disturbs the
particles in the medium perpendicular to the
direction of the wave’s travel.
2. Longitudinal Waves: A wave that disturbs the
particles in the medium parallel to the direction of
the wave’s travel.
Transverse vs. Longitudinal Waves
Checkpoint
1.
What is a Transverse wave?
1.
What is a Longitudinal wave?
Slinky Demo
⚫How can a single transverse wave pulse be produced
using a slinky?
⚫How can a single longitudinal wave pulse be produced
using a slinky?
⚫ Sound waves are longitudinal waves because they shake
the air as they transfer the energy to our ears.
Must Watch Television
⚫https://www.youtube.com/watch?v=XFF2ECZ8m1A
Bellringer
⚫
DO
STOP
WORK
Objectives
⚫Learn about the different types of waves.
⚫Study, create, and destroy different wave types.
Grade Update
⚫Answer these questions.
1. How did you follow your plan on how to improve
your grade?
2. Are you happy with your grade and what do you
want your grade to be by the end of the quarter?
3. What are you going to do to improve your grade?
Waves at Boundaries
⚫What does the surface of water look like when you
drop a small rock in a calm bucket of water?
⚫What happens when the wave hits the walls?
⚫Splash Demo!!! Get your goggles!
Waves at Boundaries
⚫Recall that a wave’s speed depends on the medium it
passes through:
⚫ Water depth
⚫ Air temperature
⚫ Tension, and mass
⚫A “Boundary” is when a wave goes from one medium
to another.
Waves at Boundaries
⚫There are three ways you’ll be interested in at
boundaries.
1. Incident Wave: A wave pulse that strikes the
boundary.
2. Reflected Wave: A wave that bounces backwards
after hitting the boundary.
3. Transmitted Wave: A wave that continue forward
after hitting the boundary.
Waves at Boundaries
Waves at Boundaries Demos
⚫Different Medium Demo:
⚫ The incident energy is split between reflected and
transmitted energy.
⚫Rigid Boundaries Demo:
⚫ All of the incident energy is turned into reflected
energy.
Checkpoint
1.
How does the amplitude (energy) of a wave change
when it hits a rigid boundary like a wall?
1.
How is the conservation of energy observable with
a single wave hitting a different medium?
Waves in a Bucket
⚫What happens if you drop two rocks into a calm
bucket of water instead of just one?
⚫Splash Demo 2.0!!! Get dem goggles back!
⚫The waves seem to hit each other, but then just
continue on their way…weird?
Wave Interference
⚫When we had two particles (carts) and pushed them
into each other they collided and then stopped.
⚫When waves collide they temporarily interfere with
one another, but they do not stop each other.
Wave Interference
⚫The Principle of Superposition states that the
displacement of a medium caused by two or more
waves is the algebraic sum of the displacements
caused by the individual waves.
Superposition (Interference)
Now a super superposition demo!
1.
Can we make two waves create a bigger wave?
1.
Can we make two wave create a smaller wave?
1.
Is there a limit to how many waves we can create?
Bellringer
⚫
DO
STOP
WORK
Objectives
⚫Learn about the different types of interference,
practice solving problems that deal with it, and
demonstrate the different interference patterns with a
small group.
Limit to waves?
⚫The number of waves that are interfering with each
other is limitless.
⚫Each wave is just a form of a sine wave.
⚫Wolfram Alpha Demo:
⚫ https://www.wolframalpha.com/input/?i=sinx+
Types of Interference
⚫ There are three types of interference
1. Constructive Interference: When the crest of a wave
meets a crest of another wave of the same frequency at
the same point.
2. Destructive Interference: When the crest of a wave
meets a trough of another wave of the same frequency
at the same point.
3. Different Amplitude: All other scenarios of waves
interference.
Constructive vs. Destructive
⚫Which is constructive and which is destructive
interference? How do you know?
Interference Practice
⚫If waves A and B
were aligned on
top of each other,
what would the
resultant wave look
like?
Interference Practice
⚫If waves A and B
were aligned on
top of each other,
what would the
resultant wave look
like?
Interference Practice
⚫What does the
wave look like
under the
block?
Can you do this?
⚫Let’s see if we can successfully make waves both
constructively and destructively interfere!
⚫Note: not all the slinkies are in the best shape, but
remember this is not an open invitation to make them
worse!
Can you do this?
⚫ Try to complete these 5 missions. Try to take video or
pictures with your phone to capture the interference.
1. Make two transverse waves constructively interfere.
2. Make two longitudinal waves constructively interfere.
3. Make two transverse waves destructively interfere.
4. Make two longitudinal wave destructively interfere.
5. Play around with different amplitudes, can you get three
waves to interfere?
Bellringer
⚫Draw a picture of two
waves moving towards
each other that will
constructively interfere
once their crests meet.
DO
STOP
WORK
Objective
⚫Learn and be able to identify standing waves and their
properties.
Results? – Where are they?
⚫What were you able to find?
⚫E-mail me your successful results!
⚫ KVerspoor@windsor-csd.org
⚫Were there any trials that didn’t work?
Grade Update - Labs
⚫Answer these questions.
1. How did you follow your plan on how to improve
your grade?
2. Are you happy with your grade and what do you
want your grade to be by the end of the quarter?
3. What are you going to do to improve your grade?
Homework
⚫Read pages 394 to 397.
⚫Stop before reading “Waves in Two Dimensions” on
page 397
⚫Very good illustrations and snapshots of
superposition and interference.
Standing Waves
⚫When a wave appears to just move up and down
instead of transmitting energy side to side it is called
a standing wave.
⚫These waves appear to be standing still, hence
“Standing Wave”.
Standing Wave Demo
⚫ What happens to the number of bumps as I increase
the frequency? Why?
⚫ How does the wavelength change has I increase the
frequency?
⚫How does the speed of the waves change as I increase
the frequency?
Standing Waves
⚫Why must I keep oscillate my arm to generate a
standing wave?
⚫A standing wave is made up interfering waves moving
in opposite directions. Without this small input the
wave would die out.
Standing Waves
⚫ Resonance is when a small energy input frequency is
continually applied to an object and it causes the object to
oscillate with greater and greater amplitude.
⚫ Resonance is continual constructive interference.
⚫ Every object has a resonance frequency.
⚫ Swing-sets use resonance.
⚫ Microwave ovens are the resonance frequency of water.
⚫ Tesla found the resonance frequency of the Earth.
Tacoma Narrows Bridge
⚫https://www.youtube.com/watch?v=xox9BVSu7Ok
⚫The designer took Tacoma’s money and said he
brought and insurance policy for the bridge…he didn’t
⚫The bridge started oscillating almost as soon as it was
finished.
⚫It collapsed just days before the fake insurance policy
would have expired.
⚫He went to jail.
Nodes and Antinodes
⚫Nodes and Antinodes are used to help describe and
understand waves.
⚫A “node” is where waves meet and cause zero
displacement of the medium.
⚫ No displacement
⚫An “antinode” is where waves meet and cause the
largest displacement of the medium.
⚫ Anti no displacement
Nodes and Antinodes
Nodes and Antinodes
Practice
⚫How many nodes and antinodes does the wave below
have?
FYI
⚫The mod 8 physics class is smoking the mod 2 physics
class…90 to 84!
Practice
⚫Page 403 numbers 61-63, 67, 71-74, 76
⚫17 minutes to complete.
⚫Work in pairs or groups of three.
⚫Each group can ask me up to three questions.
⚫Counts as a grade…homework? Quiz? Lab? Test?
Answers
61.
62.
63.
67.
71.
T=8.3s
4.0 m/s
v=0.288 m/s ; T=0.21s
f=550Hz ; 275 waves ; 165m
The reflected wave pulse from a rigid boundary is
inverted.
Answers
72. No displacement or movement
73. Bare areas are antinodes, sugar covered areas are
nodes
74. A standing wave exists and the string can be
touched at any of its five nodes
76. See drawing.
Bellringer – 2 mins to hand in
⚫What is a standing wave?
⚫What is an antinode?
⚫What is a node?
DO
STOP
WORK
Objectives
⚫Practice your understanding of waves.
⚫Complete “Slinky Lab” to demonstrate you have the
power to create and destroy waves.
⚫Computer simulator.
Slinky Lab
⚫All sample calculations must be shown on a separate
sheet of paper.
⚫All answers to questions must be shown on a separate
sheet of paper.
⚫All questions must be answered in complete
sentences with full explanation.
⚫1 tile is 1 meter.
Bellringer – 2 mins to turn in
⚫Turn it in on the back
table and pick up your
bellringer from last week
as well as your group’s
answers from last week.
⚫How are standing waves
created?
DO
STOP
WORK
Standing Waves
⚫What is a standing wave?
⚫How are standing waves created?
⚫What is an antinode?
⚫What is a node?
Objectives
⚫Review the basics of waves for a quiz tomorrow.
Labs
⚫Please pass up your slinky labs
Introduction to Waves Quizest?
⚫15 multiple questions?
⚫3 long answers?
⚫1 mod
⚫Tuesday?
More Drawing
⚫In the “Intro to Waves HW” packet answer questions
35 (parts 1-3), 35, 36, 37
⚫ Yes there are two number 35s
⚫For homework finish the packet!
Standing Wave Simulator
⚫What does a standing longitudinal wave look like?
⚫ https://phet.colorado.edu/en/simulation/normalmodes
⚫Fixed end vs. open end. Destructive and Constructive
Interference
⚫ https://phet.colorado.edu/en/simulation/wave-on-astring
What’s on the Quizest?
⚫Wave Vocabulary
⚫Drawing Waves
⚫Transverse vs. Longitudinal Waves
⚫Wave interference and Superposition
⚫ Constructive/Destructive
⚫Standing Waves
⚫ Nodes and Antinodes
Bellringer – 2 mins to turn in
⚫ Turn it in on the back table
and pick up your bellringer
from last week as well as
your group’s answers from
last week.
⚫ If a wave travels at 15m/s
and has a wavelength of
2.2m what is its frequency?
DO
STOP
WORK
Objectives
⚫Review the basics of waves for a quiz tomorrow.
Intro to Waves HW
You be the teacher!
⚫You know all the topics that will be on the quizest.
Can you use this knowledge to figure out the
questions I’ll ask?
⚫Write 2 multiple choice questions and 1 long answer
question with at least 2 parts.
⚫Try to cover as many of those categories as possible.
You be the teacher!
⚫I’ll collect and redistribute the questions.
⚫Find your partner then solve the questions you are
given.
⚫Then you’ll grade their responses.
⚫Who had good questions?
Intro to Waves HW Packet
Physics teacher wave generator
⚫https://www.youtube.com/watch?v=-gr7KmTOrx0