8
Danger from the Ocean:
Describing Waves
Teacher Edition
ACKNOWLEDGMENTS FOR FOUNDATION SCIENCE PHYSICS 1 AND 2
EDUCATION DEVELOPMENT CENTER, INC. STAFF (AUTHORS ARE STARRED)
Irene Baker, Senior Curriculum Design Associate*
Erin Barder, Ph.D., Consultant*
Christine Brown, Curriculum Design Associate I
Bettina Dembek, Research Associate II
Joseph Flynn, Senior Program Director
June Foster, Project Director
Sandra Frith, Administrative Assistant
Charles Hill, Senior Training and Technical Design Associate
Erica Jablonski, Research Associate I
Ruth Krumhansl, Senior Curriculum Design Associate*
Silvia LaVita, Graphic Design Specialist I
Jacqueline Miller, Principal Investigator
Kerry Ouellet, Production Editor
Katherine Paget, Senior Research Scientist
Marian Pasquale, Senior Research Scientist
Anne Marie Walker, Developmental Editor
CONTENT REVIEWERS
Carolann Koleci, Worcester Polytechnic Institute, Worcester, MA
Jerold Steven Touger, Curry College, Milton, MA
David V. Guerra, St. Anselm College, Manchester, NH
FIELD TEST TEACHERS
Yetta Allen, Sammamish High School, Bellevue, WA
Laura Baumgartner, Robinswood High School,
Bellevue, WA
Penny Blue, Lyons High School, Lyons, KS
Jen Chesnut, Ottumwa High School, Ottumwa, IA
Dana Crudo, Johannesburg-Lewiston High School,
Johannesburg, MI
Barbara Engler, Burlingame Jr/Sr High School,
Burlingame, KS
John Giffin, Vienna High School, Vienna, IL
Sharla Hanzlik, Niobrara High School, Niobrara, NE
Lisa Henderson, TechBoston Academy, Boston, MA
Marsha Hennig, Tates Creek High School, Lexington, KY
Kim Herzog, Sammamish High School, Bellevue, WA
David Johnson, Douglas High School, Winston, OR
David Kelso, Manchester Central High School,
Manchester, NH
Katie Klug, Newport High School, Bellevue, WA
Ethel Locke, Woonsocket High School, Woonsocket, RI
Frankin Mansilla, Madison Park High School,
Boston, MA
James McIntyre, Bellevue High School, Bellevue, WA
Matthew Misci, Sea Coast Middle/High School,
Revere, MA
Thomas Mulhern, Hillside High School, Hillside, NJ
Deborah Pusateri, Ursuline Academy, New Orleans, LA
Stephanie Rico, San Diego High School, San Diego, CA
Jeff Rierson, Interlake High School, Bellevue, WA
Chad Ronish, Hill City High School, Hill City, SD
Megan Scanderbeg, Stelle Canyon High School, Spring
Valley, CA
Matthew Sly, Urbana High School, Urbana, IL
Chris Stevens, Linus Pauling Academy at Marshall High
School, Portland. OR
Paula Weinspach, Chapin High School, Chapin, SC
Jeffrey Wolovitz, Georges Valley High School,
Thomaston, ME
This material is based upon work supported by the National Science Foundation under Grant No. 0439443. Any opinions,
findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily
reflect the views of the National Science Foundation.
© 2012 Education Development Center, Inc.
Teacher Edition
8
Danger from the Ocean: Describing Waves
Overview
Waves are the transfer of energy from one place to another. Although most students will already
be familiar with waves, they may struggle with the concept that energy can travel through a
medium without causing a net movement in the particles that make up that medium. In water
waves and other mechanical waves, matter moves periodically (e.g., back and forth, side to side,
elliptically) as the wave travels through it, but at the end of the motion, the matter returns to the
place at which it began.
There are many kinds of waves; this learning experience focuses on water waves. Students begin
the learning experience by brainstorming what they already know about waves—what waves are,
how they are formed, and how they travel. Students read about the Indian Ocean tsunami that
occurred in December of 2004. They are then asked to role-play interns who are assisting a
movie company that is creating a movie about the tsunamis. The Challenge for students is to
provide guidelines about the behavior of waves. As students prepare to meet the Challenge, they
explore how waves form, the different kinds of waves, and how waves interact with obstacles
and each other.
Goals for Student Understanding
•
Students understand that waves are the movement of energy through matter or through space.
•
Students understand that waves that travel through a medium include the movement of the
wave itself, which is called propagation, and the movement of the particles of the medium,
which is called vibration.
•
Students understand that collisions between the vibrating particles are the mechanism by
which energy travels through a medium.
•
Students understand that waves are transverse if their particles’ vibration is perpendicular (at
right angles) to the wave’s travel, longitudinal if their particles’ vibration is parallel (in the
same direction) to the wave’s travel, and combination if their particles’ vibration is elliptical
(oval). The elliptical motion of the particles of combination waves is due to the fact that they
are vibrating in both parallel and perpendicular directions.
•
Students know that the end points of the path of vibrating particles in a transverse wave are
called crests and troughs, and that the end points of the path of vibrating particles in a
longitudinal wave are called compression and rarefaction.
•
Students know that two measurements of waves are the amplitude, which is the displacement
of a vibrating particle from its undisturbed position to its maximum position, and the
wavelength, which is the displacement between similar points on two adjacent waves.
•
Students understand that a wave can change direction in three ways. Reflection occurs when
a wave bounces back from a surface it cannot pass through. Refraction occurs when a wave’s
path is bent because it changes velocity as it moves from one medium to another or when the
©2012 Education Development Center, Inc.
8-1
•
medium changes. Diffraction occurs when a wave bends around an obstacle or goes through
an opening.
Students understand that interference occurs when two waves meet each other. Students
understand that although the two waves pass through each other, at points of constructive
interference, the new wave has an amplitude equal to the sum of the two amplitudes, and at
points of destructive interference, the new wave has an amplitude of zero if the two waves
are of equal size.
Student Assessment Outcomes
Students should be able to:
•
Explain that waves involve the transfer of energy but not matter and give an example of a
situation in which this occurs
•
Define propagation and vibration
•
Distinguish among examples of longitudinal, transverse, and combination waves
•
Recognize the following features of transverse waves: crest, trough, amplitude, and
wavelength
•
Explain that the wavelength of a transverse wave is the displacement between two adjacent
crests
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Recognize examples of reflection
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Recognize examples of refraction
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Recognize examples of diffraction
•
Recognize examples of interference
Assumptions of Prior Knowledge and Skills
Students should already know:
•
That energy can be transferred from one object or place to another object or place
•
How to follow procedures, observe carefully, and record observations
Possible Misconceptions and Barriers to Learning
•
Many students may believe that waves transport matter from one place to another.
•
Many students may believe that waves must have a medium.
•
Many students may believe that because waves do not transport matter, they have no energy.
•
Many students may not understand that features of waves depend upon the medium through
which the wave is traveling.
•
Many students view waves as an object and not as an event.
•
Many students may describe a wave only by its crest.
•
Many students may believe that a wave’s amplitude influences its speed.
Assessment Strategies
Students have a number of opportunities in this learning experience to express their initial and
developing understanding of concepts related to waves. By taking note of the answers given by
students completing group work or working individually, you can determine pacing, identify
which concepts need more or less emphasis, and gauge students’ understanding of the content at
the end of the learning experience. These formative and summative assessment opportunities
include:
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Foundation Science: Physics 1 Teacher Edition
Opportunities
Consider
Brainstorming
Think About What You Read for
The Deadliest Tsunami in History?
Investigate
Think About What You Read for
Waves
Activity 1 Procedure
Activity 1 Analysis
Think About What You Read for
Understanding Wave Interactions
Activity 2 Procedure
Activity 2 Analysis
Address the Challenge
Information Gathered About
Students’ initial ideas about how waves are formed and
how they transfer energy.
Students’ ability to summarize descriptive information
about the waves in the story.
Students’ ability to explain how particles of the medium
move in each wave type.; students’ ability to explain crest,
trough, amplitude, and wavelength.
Students’ ability to create and observe different kinds of
waves.
Students’ ability to describe different wave shapes and
how the waves form and move.
Students’ ability to distinguish different kinds of wave
interactions.
Students’ ability to create and observe wave interactions.
Students’ ability to describe the interactions that waves
undergo when they hit obstacles, or the medium changes,
or they meet other waves.
Students’ ability to apply what they learned about wave
behavior to real-life scenarios.
Process
Share
Discuss
Assessment
Students’ share their ideas on how waves behave in the
real-life scenarios.
Students’ discuss the reasons for differences in their
responses about the real-life scenarios.
Students’ understanding of the range of concepts presented
throughout the learning experience. These questions can
be used in class, for homework, or as a quiz at the end of
the learning experience.
You should determine ahead of time which of these assessment opportunities you will evaluate
formally (i.e., by assigning a grade) and which you will evaluate more informally.
Suggested Class Sessions
8 class sessions (45 minutes each)
Materials and Preparation
Prior to Activity 1
1. Gather the following for each group of students:
•
wave tank (or any large, shallow, clear container) with 5 cm of water
•
ruler
•
dark food coloring
•
thin elastic cord about 2 meters long
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8-3
•
•
2 regular Slinkies attached together to form one long double Slinky
a table long enough to hold the double Slinky
2. Obtain internet access for your class to view some animations of wave motion. Two sites that
have animations are http://www.gmi.edu/~drussell/Demos/waves/wavemotion.html and
http://www.physics.northwestern.edu/vpl/waves/wavetypes.html.
3. Set up your classroom to accommodate the activities.
•
For Part A, students will need enough room for the whole class to sit in a circle.
•
For Part B, the whole class will need to be able to observe a demonstration carried out by
two student volunteers.
•
For Part C, each group of students will need access to a table that is long enough to
accommodate two Slinkies attached together to form a double Slinky.
4. You will need wave tanks for each group. Plastic frames used for special types of picture
framing like shadow boxes can be substituted if you do not have wave tanks. If materials are
limited or you do not have a large water supply or disposal means, carry out the wave tank
activities as demonstrations.
5. Review the materials lists in all activities to prepare special setups.
Prior to Activity 2
1. Gather the following for each group of students:
•
wave tank or shallow, rectangular, clear plastic or glass container with water at 1 cm in
height (the water can have a few drops of food coloring added to it for easier viewing)
•
semi-stiff ruler
•
clear circular dish (such as glass pie plate or plastic, plant pot protector) with water at 1
cm in height (the water can have a few drops of food coloring added to it for easier
viewing)
•
pencil with eraser (new)
•
7–10 small blocks of wood that are higher than 1 cm and can be placed in water
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large block of wood that is slightly higher than the edge of the rectangular wave tanks
•
clear sticky tape
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water to fill the wave tank to a depth of 1 cm
•
scoop
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silly putty (enough to make two moderate-sized balls)
•
several paper clips
2. Set up your classroom to accommodate the activities.
•
For Parts A–D, students will need space to work in their groups with wave tanks.
•
For Part E, use masking tape to mark off a cleared floor-space at least 3-meters square,
and then lay down a 3-meter strip of tape at an angle within the square
Prior to Address the Challenge
1. Gather the following:
•
lined and blank paper
•
rulers
•
pencils
•
wave tanks and other materials used in Activity 2
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Foundation Science: Physics 1 Teacher Edition
2. Develop and explain a rubric for your students for grading their work.
Teaching Sequence Preview
Consider
•
Students describe their understanding of waves, list the ways they think waves are formed,
and speculate on how waves travel long distances.
•
Students read a story that describes a deadly tsunami and summarize from the story
information about the cause and behavior of the tsunami waves.
Investigate
•
Students are introduced to the Challenge: to help a movie company create realistic computeranimations of waves by explaining how waves act in real-life scenarios.
•
Students read about wave movement, three categories of wave types (transverse,
longitudinal, and combination waves), and about features and measurements of waves.
•
Students observe in several contexts that wave motion does not involve the overall
movement of the medium that the wave travels through.
•
Students create transverse, longitudinal, and combination waves.
•
Students read about how waves interact with their environment and with each other. Students
learn about reflection, refraction, diffraction, and constructive and destructive interference.
•
Students observe and analyze what happens when: waves hit a solid wall; waves move
around an obstacle or through an opening; waves from two sources meet each other; and the
medium that the wave is traveling in changes.
•
Students role-play science-savvy interns working for a movie company that is creating a
movie about the tsunami. Students work in groups and prepare a report that answers
questions about wave behavior in real-life scenarios. The report has both text and pictures.
Students have access to the readings, to their notes, and to wave tanks while they prepare
their report.
Process
•
Students share their group’s answers with the rest of the class. As each group presents, other
students listen and take notes.
•
Students discuss any differences among the answers given by different groups about the reallife scenarios.
Consider
Purpose
The activities in this section are designed to draw out students’ prior knowledge of waves and
provide a context that engages students in learning about waves.
Begin by having students read the learning experience introduction, and then have them work
with a partner to respond to the Brainstorming questions.
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Possible Responses to Brainstorming
Students may not have all the answers to these questions; however, their responses will provide
insight into their prior understandings about waves. Inform them that they will be returning to
many of these ideas in the learning experience.
1. What do you already know about waves? Try to describe how waves start, their shape, and
how they act. Answers will vary and will likely depend on students’ prior instruction.
Teaching Strategies
You may need to discuss the many colloquial uses (nouns and verbs) of the word wave. Like many words
used in physics, wave has both scientific and nonscientific meanings. Some of the nonscientific meanings
of waves include
• a movement like that of a sudden occurrence or increase in a specified phenomenon—a wave of
settlers; troops advancing in waves;
• something that rises rapidly—a wave of emotion swept over him; there was a sudden wave of buying
before the market closed; a wave of conservatism in the country led by the hard right;
• the act of signaling by a movement of the hand;
• brandish: move or swing back and forth—she waved her gun;
• an undulating curve;
• a persistent and widespread unusual weather condition (especially of unusual temperatures)—a heat
wave;
• set waves in—she asked the hairdresser to wave her hair.
2. What kinds of events cause water waves to form? For water waves, students may mention
wind or a rock dropping in the water. For sound waves, students may mention speakers or
musical instruments. Some students may have the misconception that waves are a property of
water independent of an event that causes it.
3. How do you think energy is involved in a wave? Answers will vary.
Teaching Strategies
Tell students that it is OK to speculate about how energy is involved in a wave. You may want to post
their current ideas now, and then later on post the description of how a wave travels after students
complete the first reading in Investigate, which describes the transfer of energy in a wave.
4. Think about water waves you have seen. What happens to the water as the wave moves
through it? Answers will vary. Some students may have the misconception that the water
moves along with the waves.
5. What do you know about tsunamis? What tsunamis have you heard about? Answers will
vary. Due to publicity about tsunamis, students may have learned a lot about tsunamis and
may have read about recent tsunamis that have occurred.
6. Water waves are one kind of wave. What other waves can you name? Answers will vary.
Students may answer based on prior study of waves in science or based on their
understanding of a wave.
WHAT’S THE STORY? Killer Tsunami
This story is about the tsunami that occurred in the Indian Ocean in December of 2004. It
provides an account of the energy contained in waves.
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Foundation Science: Physics 1 Teacher Edition
Responses to Think About What You Read for Killer Tsunami
1. What was the underlying cause of the tsunami? An earthquake was the underlying cause.
2. What was the amount of energy associated with that event? The total energy of the movement
of the tectonic plates and ocean was about 370 times the energy used by the entire United
States in the year 2005.
3. What is the speed of the tsunami waves? They travel through the ocean at speeds of 500 to
1,000 kilometers per hour (310 to 620 miles per hour).
4. How far did the tsunami waves travel? The waves that did not hit land traveled about 19,500
kilometers (12,000 miles).
5. Is a tsunami noticeable in the open ocean? Why or why not? No, because the tsunami waves
may be less than a foot (30 centimeters) high in the open ocean.
6. What happens to the tsunami waves when they approach land? The shallow depths slow the
waves down and the waves become much higher.
Investigate
Purpose
Students are presented with activities and readings that can help them make sense of concepts
related to waves.
Introduce the Challenge—students will role-play science-savvy interns who will explain how
waves act in several real-life scenarios in order to help a movie production company make a
movie that shows the tsunami.
GATHER KNOWLEDGE
Students will work in groups of three to four in the activities in this section.
READING: Waves
The vocabulary terms wave, medium, propagation, vibration, transverse wave, longitudinal
wave, combination wave, crest, trough, amplitude, and wavelength are defined in the reading.
Review the reading and the Think About What You Read questions.
Responses to Think About What You Read for Waves
1. What is the movement of wave over a distance called? What is actually moving? The
movement of a wave over a distance is called propagation. Energy is moving.
2. When a material medium is needed for a wave to travel, what is the movement of the
particles of the medium called? The movement of the particles of the medium is called a
vibration.
3. In water, the crest of a wave can pass under a floating object and raise it up, but the wave
crest does not carry the object continuously forward. Explain why. The water doesn’t move to
another location. When a wave passes through a section of water, its particles vibrate but
return to their original position.
8: Danger from the Ocean: Describing Waves
8-7
4. Describe the three different kinds of waves and explain the movement of the particles in each
compared to the direction in which the wave travels. The direction of the vibration of the
medium causes different shapes of waves to form. Transverse waves move up and down or
side to side because its parts vibrate at right angles to the direction of wave travel.
Longitudinal waves expand and contract because their parts vibrate along the same
dimension as the direction of wave travel. Combination waves move in an elliptical
movement because their parts are moving both side to side and back and forth.
5. What feature of waves is described by a wave’s crest and tough? These points show the
maximum displacement of the particles in a wave.
6. How is the amplitude of a transverse wave related to the wave’s crest? The amplitude is the
displacement between a wave particle’s undisturbed position and crest.
7. What feature of waves is described by wavelength? Wavelength measures the displacement
between similar points on two adjacent waves.
ACTIVITY 1: Investigating How Waves Form
In this activity, students have an opportunity to see firsthand what kinds of action can cause a
wave to form and how a wave moves. To confront the perception that a wave involves the
movement of a medium, students will observe in several contexts that wave motion does not
involve the overall movement of the medium but instead involves a periodic movement of parts
of the medium—such as back and forth, or side to side, or elliptical movement. The activity is
divided into three subactivities—a class activity, a demonstration, and a group activity.
Facilitate the Activity
Part A: The Wave
•
Encourage students to talk about how a wave moves before you begin. Most students will
think that a medium moves with the wave.
•
Have students answer the Analysis questions and prepare for a discussion. Responses for the
questions in the three different procedures are found in the next section.
Part B: Is the Water or the Wave Moving?
Ensure that many students state their predictions. Have students give their reasons for their
predictions as well.
•
Review the safety notes with students.
•
Once students see that the food coloring doesn’t move, encourage them to reevaluate their
ideas about how a wave moves. Have students make the connection to The Wave activity
preceding this demonstration.
•
Have students answer the Analysis questions and prepare for a discussion. Responses for the
questions in the three different procedures are found in the next section.
•
Part C: Creating Waves
•
Review the safety notes with students.
•
Working with Slinkies takes a certain amount of dexterity and practice. You may choose to
have several students who are particularly adept at creating waves demonstrate the waves.
•
Circulate to groups and discuss the wave shapes with them.
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Foundation Science: Physics 1 Teacher Edition
•
•
Review the Think About It questions with students. Students should begin to see that the
medium returns to its original position after the waves pass through it.
Have students answer the Analysis questions and prepare for a discussion. Responses for the
questions in the three different procedures are found in the next section.
Responses to Analysis for Activity 1: Investigating How Waves Form
Part A: The Wave
1. Explain how the movements were coordinated so that the wave appeared to be moving
around the room. The first person’s arms were raised, and then the next person’s arms were
raised right afterwards, and so on, which made the wave appear to move around the room.
Interaction—in this case visual communication—between each person and the next was
needed.
2. Describe the shape of the wave. It varies from a high point to a low point as people stand up
and sit down. The high point travels around the room because each person is standing up
one after another.
Part B: Is the Water or the Wave Moving?
1. Compare the movement of the food coloring with the movement of the wave. The food
coloring spreads out slightly in all directions but is not affected by the waves moving through
it.
2. What does this demonstration show about the movement of water during the wave? The
water doesn’t move along with the wave.
3. What is similar about the water in a water wave and the people in a stadium wave? In both
cases, as the waves travel, the medium through which the wave travels moves but the medium
does not travel. People move up and down, and the water moves up and down, but neither
travels along with the wave.
Part C: Creating Waves
1. For the transverse wave, compare the direction of motion of the cord with the direction in
which the wave traveled. The cord was moving side to side (or up and down) while the wave
moved forward.
2. For the longitudinal wave, compare the direction of motion of the coils with the direction in
which the wave traveled. The Slinky was moving forward and backward while the wave
moved forward.
3. For the combination wave, compare the direction of motion of the water with the direction in
which the wave traveled. The water was moving up and down while the wave moved forward.
Teaching Strategies
Point out to students that there is an oval motion of water parts and that this motion is reflected by both
an up and down and a back forth motion of an object floating on top of a wave. However, the up and
down motion is usually more prominent.
4. How was the energy from the initial shaking or push transmitted along the wave medium (the
cord, Slinky, or water)? Cord: The cord was stretched at the site of the initial pluck and then
tightened in response because of elastic force. The tightening of one section in turn stretched
the next section, and so on. Slinky: One section of the Slinky was squished and then pushed
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8-9
back, and this in turn squished and then pushed back another section, and so on. Water:
Some water was displaced upward and then moved downward and forward. The water
moving downward and forward in turn caused the next section of water to be displaced
upward, and so on.
Teaching Strategies
Remind students that when they did the wave in the first activity, the interaction that caused the wave to
pass from student to student was visual. Then explain that in every wave there must be an interaction or
a mechanism that causes the wave to propagate.
READING: Understanding Wave Interactions
The vocabulary terms reflection, refraction, diffraction, interference, constructive interference,
crest, destructive interference, and trough are defined in the reading. Review the reading and the
Think About What You Read questions.
Responses to Think About What You Read for Understanding Wave Interactions
1. Review Figure 8.5. What aspects of the wave are changed after it reflects? The only thing
that changes is the direction of the movement of the wave.
2. Compare and contrast refraction and diffraction. Both involve the wave changing direction.
Refraction occurs with a change in medium. Diffraction occurs when there is a partial
obstacle.
3. When light enters a prism or lens, the light bends. What type of wave interaction is
occurring? Refraction.
4. Some musical venues have seats where the sound is very low and other seats where the sound
is very loud. What type of wave interaction causes this effect? Explain your reasoning.
Interference between sound reaching you directly from the performer and sound reflecting
from the walls, ceiling, and so on can be constructive or destructive, and so can cause this
effect. At particular points, the combined disturbance produced by the direct and reflected
waves can be bigger or smaller.
ACTIVITY 2: Describing the Interactions of Waves
Students observe different kinds of wave interactions: waves hitting a wall, waves moving
around an obstacle or through an opening, waves from two directions meeting each other, and
waves moving from one medium to another. These observations will help students understand
the behavior of waves in different situations. The activity is divided into five short
subactivities—four group activities using water tanks and a class activity.
Pre-Activity Discussion
Ask students to think of a beach/coast setting and to brainstorm how waves behave when they
come ashore and hit obstacles such as rocks, piers, boats, and so on.
Facilitate the Activity
• Review the safety notes with students.
• Have materials on hand to clean up any water spills. You may want to cover the tables with
newspapers as well.
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Foundation Science: Physics 1 Teacher Edition
•
•
•
•
•
Because students are working with water, make sure that any books, notebooks, papers, and
so on are set aside during the actual lab activities.
Help students connect their observations of the water tank to real-life water waves they have
observed.
You may want to set time limits on each activity, and then review the Analysis questions with
the whole class using an overhead projector or computer screen projector.
In Part E, have students stop when they get too close together.
Have students answer the Analysis questions and prepare for a discussion.
Responses to Analysis for Activity 2: Describing the Interactions of Waves
Part A: Plane Waves Reflection
1. When the waves were moving parallel to the wall of the container, what happened when the
waves hit the wall? They bounced straight back (they reversed their direction).
2. When the waves were moving at an angle to the wall of the container, what happened when
the waves hit the wall? What can you conclude about the angle at which the waves bounce
off the wall? They hit the wall at an angle and bounced off at the same angle, but in the other
direction.
Part B: Circular Waves Reflection
1. What was the difference in how the waves formed when you tapped the pencil in the center
compared to when you tapped slightly off center? Offer an explanation for how circularshaped waves act when you tap slightly off center. When the pencil was tapped in the center,
the wave bounced back from the edge and returned to the center. When the pencil was tapped
slightly off the center, the wave came back to a point that was opposite to where the pencil
was tapped. This happened because the part of the wave that started closer to the edge
bounced off and traveled past the starting point. The part of the wave that started farther
from the edge bounced off and traveled back but did not have time to get back to the starting
point because it met the part of the wave that had already reflected and come back past the
starting point.
2. A standing wave has vibrations or oscillations that don’t appear to travel. Was anyone in
your group able to create a standing wave? What do you think might cause this effect? The
waves interfere with each other in such a way that the crests and troughs of the new wave
and the reflected wave are always meeting in the same place. When the crests of the reflected
waves meet the crests of the oncoming waves, they combine to create higher crests. When the
troughs of the reflected waves meet the troughs of the oncoming waves, they combine to
create lower troughs.
Part C: Plane Wave Diffraction
1. Describe the three patterns you saw when you made the water pass through small openings.
The wave bent to one side when the opening was on one side. The wave became a half circle
when it went through the small opening. The waves bent around and inward when going
around the obstacle in the middle of the tank.
2. In what way did the direction of the wave change in each case? It changed direction so that it
was going in more than one direction at once.
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Part D: Circular Wave Interference
1. Describe the waves created by each Silly Putty ball. The waves are circular waves.
2. What do you see happening when the waves from each ball cross over each other? Try to list
more than one observation and propose an explanation for what you observe. Students may
have a number of observations. Some observations include the following: the waves passed
through each other. They formed diamond shapes in the water when they crossed each other.
In some places in the water, the up-and-down motion was pronounced. At other locations,
there was little or none. These locations seem to alternate along lines fanning out from the
midpoint between the two balls. Explanations about the pronounced nature of the up-anddown movement may refer to the fact that two waves are interacting with each other.
Part E. Human Wave Refraction
1. Did the wave change its direction? If so, how? At each point in time, the part of each row
(each wave front) that was already across the tape had bent. Also, the rows that hadn’t
crossed the tape had gained on the rows that had. Overall, the bent rows that were already
across the tape and the unbent rows that hadn’t reached the tape formed a fan shape.
2. When the wave reached shallower water, what happened to the waves that were coming
behind it? What occurred? The waves slowed down in shallower water. The waves bunched
up because the faster waves caught up with the slower waves.
ADDRESS THE CHALLENGE
Working in groups, students describe wave behavior in words and pictures in response to a list of
questions addressed to them by the movie production staff.
Facilitate Address the Challenge
• Before students work together in a group, have students individually review the notes they
made during each of the two activities, read the questions in the “Advising the Movie
Production Staff” section, and jot down their preliminary ideas on how to answer them.
• Encourage groups to work together on identifying the information they have learned to help
answer each question.
• Drawings will be most useful to the production team, so encourage students to create as many
drawings as possible.
• Encourage students to use the vocabulary about waves that they learned and to include
definitions of wave characteristics and behavior in their answers. Point out that this will be
needed by the production staff as it continues to work on the wave footage.
Process
Purpose
Students share their ideas about how to describe wave behavior in the situations posed by the
movie production company. Students continue to gain familiarity with the vocabulary associated
with different kinds of wave interactions, and by discussing differences in their ideas, help to
clarify their understanding of wave behavior.
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Foundation Science: Physics 1 Teacher Edition
SHARE
Have students from each group share the answers to the questions posed in Address the
Challenge.
Listening for Understanding
As students share their ideas, you should hear them explain, describe, or report some or all of the
following.
•
Students explain that when a disturbance occurs in the open ocean, the disturbance radiates in
all direction through the water. Students understand that the waves that result are the
movement of the energy of the disturbance and not the movement of the water itself.
•
Students explain that in the open ocean, tsunami waves are not distinguished by their height
but by their great speeds.
•
Students explain that a floating object does not travel with the waves but stays roughly at the
same position. Students describe the movement of the floating object as waves pass under it
as a steady and slight forward and back motion that relates to the elliptical motion of water
particles in the wave.
•
Students explain that refraction occurs when a wave bends because it changes velocity as it
moves from one medium to another or when the medium changes. Students identify the
situation when refraction occurs, which is when waves approach the shore at an angle,
•
Students explain that diffraction is when a wave bends around an object or goes through an
opening. Students identify the situation when diffraction occurs, which is when waves bend
around a building.
•
Students explain that reflection is when waves bounce back from a surface it cannot pass
through. Students identify the situation when reflection occurs, which is when waves bounce
off a cliff.
•
Students explain that when two waves pass through each other they undergo interference,
which is the addition of the two waves’ amplitudes at each point where they are crossing.
Students describe how the addition of waves’ amplitudes at different points results in lower
and higher amplitudes, depending on the heights of the two waves at that point. Students also
explain that after waves interfere with each other they continue on unchanged.
DISCUSS
To ensure that students understand the wave concepts introduced, have students share their
responses to the Discuss questions.
Possible Responses to the Discuss Questions
1. Discuss any differences among the answers given by different groups in completing the
challenge. Answers will vary.
2. The production staff will film a small-scale scene that includes water waves hitting model
buildings on a model beach. Will this scene look realistic? Why or why not? What factors
will need to be taken into account to cause the waves to look like a tsunami? The waves
would look realistic because the waves undergo refraction, reflection and diffraction at both
scales. Factors that should be taken into account can include the following. The production
8: Danger from the Ocean: Describing Waves
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staff should ensure that the underwater section is like an actual sea bottom. The production
staff should generate waves with enough speed so that they will start small and grow to a
much larger size when they hit the shore.
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Foundation Science: Physics 1 Teacher Edition
Answers to Assessment
The Assessment questions can be used to assess students’ understanding of the range of
concepts presented throughout the learning experience. These questions can be used in class,
for homework, or as a quiz at the end of the learning experience.
1. If a wave travels through a material, that material is called a
A.
B.
C.
D.
medium
wave
disturbance
interaction
Answer:
A
2. Which of the following is the BEST definition of a wave?
A.
B.
C.
D.
The movement of a medium
The movement of energy through matter or through space
The vibration of a group of particles in one location
The combination of a crest and a trough
Answer:
B
3. What is the definition of propagation?
Answer:
Propagation is the movement of the wave itself, which is the movement of energy.
4. What is the definition of vibration?
Answer:
Vibration is the repeating movement of the particles of the medium that the wave travels
through.
5. A sound originates 10 feet away from you. When the sound travels from its origin to your
ear, what is transferred?
A.
B.
C.
D.
air particles
air particles and energy
nothing travels when sound is made
energy
Answer:
D
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6. The particles of a wave are vibrating in the same direction as (parallel to) the overall
movement of the wave. What type of wave is this?
A.
B.
C.
D.
combination
longitudinal
transverse
water
Answer:
B
7. What is the lowest point of a transverse wave called?
A.
B.
C.
D.
trough
crest
rarefaction
compression
Answer:
A
8. When a wave travels through a medium, does the medium travel along with the wave?
Defend your answer.
Answer:
The medium does not travel with the waves. If you observe a water wave or a wave with
a slinky, you see that the medium is disturbed but that it also returns to its original
position after the wave has passed.
9. Match each of the following terms in the left column with its correct definition in the right
column. There is one extra definition in the list that will not match any of the terms.
A. Wave
B. Vibration
C. Transverse wave
D. Longitudinal wave
E. Combination wave
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I. A wave that has particles vibrating in an up-anddown motion that is perpendicular to the overall
wave motion
II. A repeating vibration or oscillation that occurs in
successive parts of a medium, and resulting in the
transfer of energy
III. A wave that has particles vibrating in a back-andforth motion that is parallel to the overall wave
motion
IV. Repeated up and down, back and forth, or
elliptical motion of an object that continually
Foundation Science: Physics 1 Teacher Edition
returns the object to its starting point
V. The time it takes to complete one cycle of a wave
VI. A wave that has particles vibrating in an elliptical
motion
Answer:
A. II.
B. IV.
C. I.
D. III.
E. VI.
10. Which of the following is the best example of a wave?
A.
B.
C.
D.
a stone rolling downhill
a vehicle traveling on a bumpy road
a guitar string moving back and forth
a grasshopper jumping up and down occasionally
Answer:
C
11. Explain how wavelength is used to describe a wave.
Answer:
The wavelength is the displacement from similar points on two adjacent waves.
12. How would you measure the wavelength of a transverse wave?
Answer:
Measure the displacement from crest to crest of two adjacent waves. (Or students may
choose any other corresponding points on two adjacent waves.)
13. How would you measure the wavelength of a longitudinal wave?
Answer:
Measure the displacement from maximum compression to maximum compression of two
adjacent waves. (Or students may choose any other corresponding points on two adjacent
waves.)
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14. On the wave shown below, mark the wave’s crest, trough, amplitude, and wavelength. Be
sure to show the length of the amplitude and wavelength.
Answer:
15. Match each of the following terms in the left column with its correct definition in the right
column. There is one extra definition in the list that will not match any of the terms.
A.
B.
C.
D.
Reflection
Refraction
Diffraction
Interference
Answer:
A. II.
B. III.
I.
II.
III.
IV.
The process where two waves meet each other
The process of a wave bouncing off a boundary
The process of a wave bending as it crosses a boundary
What happens when a wave bends around objects or through
holes
V. A word that means the same as oscillation
C. IV.
D. I.
16. Look at the following pictures. Label each as an example of reflection, refraction, or
diffraction.
A
Answer
Refraction
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Foundation Science: Physics 1 Teacher Edition
Answer
Diffraction
B
Answer
Reflection
C
Photos (from top to bottom): fcarucci/Shutterstock.com; Lynne Carpenter/Shutterstock.com; Patryk Kosmider/Shutterstock.com
17. Which of the following best describes what happens when a water wave hits a solid wall?
A.
B.
C.
D.
reflection
refraction
diffraction
interference
Answer:
A
18. Consider the following diagrams, which show two waves passing through each other. Arrows
show the direction in which the two waves travel.
8: Danger from the Ocean: Describing Waves
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Explain why there appears to be no wave in Time 2 using what you know about interference.
Answer:
Because the waves are offset, they interfere destructively. As the two wave pulses meet,
their crests and troughs balance each other out. The two waves never cease to exist, so as
they move through each other the two pulses reemerge.
19. Tsunamis have a large wavelength and a small amplitude. They are dangerous when they
approach land and their amplitude becomes much larger. A wave that is dangerous in the
open ocean is a rogue wave, which has a large amplitude. Rogue waves have been known to
sink ocean-going ships. While normal waves can reach 15 meters (49 feet) in height from
trough from crest in extreme conditions, rogue waves are double this height—30 meters,
which is almost 100 feet. The cause of rogue waves is still being debated and some scientists
think there may be several different causes. Using what you learned about wave interactions,
propose one possible cause of rogue waves.
Answer:
If two waves come together with constructive interference, the resulting crest would be as
high as both the waves added together. Even a ship that could easily ride over a single
wave could be wrecked by this much larger wave.
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