IIT/FIELD MUSEUM—High School Transformation Project
Lesson: Doppler Effect with Sound Waves
Prentice Hall Conceptual Physics
Unit 4 Sound and Light
Chapter 25 Vibrations and Waves
Section 25.9 The Doppler Effect
Section 25.10 Bow Waves
Section 25.11 Shock Waves
Guiding question
How does the motion of the sender of a sound wave relative to an observer affect the frequency of
the sound wave as perceived by that observer?
Context of Lesson
This laboratory investigation will be used to explore the Doppler Effect with sound waves. Students
will witness the Doppler Effect firsthand, and graphically represent the pattern of waves that
produce the Doppler Effect. Students will have previously investigated the properties of sound
waves, including speed, frequency, and wavelength. Students will have studied the Doppler Effect
of light waves as evidence of the expansion of the universe. This lesson will give context to these
concepts of waveform interaction.
Main Goals/ Objectives:
Students will draw representations of sound waves propagated by sources in various states of
motion. The drawings will be analyzed to show the relative wavelengths of the sound waves as
they reach the observer. The relationship will be used to illustrate how sound waves propagate
outwards from both a static and a moving source.
Students will:
 Draw representations of sound waves of constant frequency from a static source
 Recognize that the wavelengths of sound emanating from this static source remain
constant throughout the area of propagation
 Draw representations of sound waves of constant frequency from a source in
motion.
 Recognize how the wavelengths of sound emanating from this source change
depending on the location of the observer in the area of propagation
In addition, students will be able to:


Understand that they are making both observations and inferences about the
nature of sound, and that modeling of a phenomenon such as sound has certain
uses and limitations.
Articulate that the observation of Doppler Effect is by its very nature subjective,
based on the physical location of the observer.
General Alignment to Standards
STATE GOAL 11: Understand the processes of scientific inquiry and technological design to
investigate questions, conduct experiments, and solve problems
A. Know and apply the concepts, principles and processes of scientific inquiry.
 ILS 11.A.4a Formulate hypothesis referencing prior research and knowledge
 ILS 11.A.4b Conduct controlled experiments or simulations to test hypotheses
 ILS 11.A.4c Collect, organize and analyze data accurately and precisely
 ILS 11.A.4e Formulate alternative hypotheses to explain unexpected results
STATE GOAL 12: Understand the fundamental concepts, principles and interconnections of the life,
physical and earth/space sciences.
D. Know and apply concepts that describe force and motion and the principles that
explain them.

ILS 12.G.1c Identify ways of production and travel for heat, light, and sound in various
media
STATE GOAL 13: Understand the relationships among science, technology and society in historical
and contemporary contexts.
A. Know and apply the accepted practices of science.

ILS 13.A.5a Design procedures and policies to eliminate or reduce risk in potentially
hazardous science activities.
PSAE Goals:
STANDARD 11A – SCIENTIFIC INQUIRY


11.11.01 Understand and follow procedures relating to scientific investigations,
including understanding the design and procedures used to test a hypothesis,
organizing and analyzing data accurately and precisely, producing and interpreting
data tables and graphs, performing appropriate calculations, applying basic
statistical methods to the data, identifying appropriate conclusions, making
predictions, and evaluating competing models.
11.11.02 Distinguish among the following: observing, drawing a conclusion based on
observation, forming a hypothesis, conducting an experiment, organizing data,
comparing data.
Materials
Per student:
1 plastic drawing compass
1 pencil
3 sheets plain paper
The Lesson
This lesson should be completed in one 45-minute class period. The teacher will demonstrate the
Doppler Effect for the students; demonstrate the technique for drawing the circles representing
the sound waves; and give instructions so that the students may complete the assignment.
Day 1
Bell Ringer
Ask students to describe what they perceive when an ambulance passes them.
Write on the board “What do you hear when an ambulance approaches? What is different about
what you hear when the ambulance passes you?” Students can write their responses in one or two
sentences.
Encourage students to try to answer the question even if they are not sure about it.
Demonstration of the Doppler Effect
Materials: small 9 volt beeper, foam ball or block, string
Assembly: Attach string to ball, cut ball open, turn on beeper, insert beeper into ball, tape shut
Demonstrate that a stationary object emitting a sound with a constant frequency is perceived to
have the same pitch. This should seem obvious, but it is shown to contrast with the next part of
the demonstration. Swing the ball in a circular motion around the students so that the ball passes
directly over the students’ heads. Move about the room so all students can hear the effect of
changing pitch as the ball passes over their head. The students should notice that they hear a high
pitch sound as the ball approaches, and a lower pitch sound as the ball recedes. Repeat this
procedure again, but this time, ask the students to focus on the sounds that the ball makes without
looking at the ball. The students should be able to tell when the ball is approaching or receding
without looking at the ball.
Activity introduction
Ask the students to describe what is happening to the sound waves when they are leaving a moving
source in the direction of motion, what is happening to the sound waves when they are leaving a
moving source opposite the direction of motion, and what would happen if the object were moving
at the speed of sound. Explain that scientific knowledge should be based on empirical data and not
only on the motion of a hand or spring pushing an object, which can vary greatly.
Lab activity
Distribute compasses and worksheets to students. Everyone can draw the sound wave diagrams
together. Draw four sets of drawings of concentric circles on a transparency sheet for overhead
projector. (Refer to Hewitt, Chapter 25, section 9.) Draw a set in advance, and draw another set
in order to demonstrate for the students as they draw. Encourage students to make multiple
drawings for each set, as the students’ drawings will generally improve greatly with practice.
Draw set 1 with 5 circles, all with a common center. Use equal spacing between the
circles, 10 mm apart. This pattern represents sound waves emanating from a static source.
Indicate verbally that the circles represent the peak in the waveform, and that the
distance between the circles represents the wavelength.
Draw set 2 with 5 circles, all with a different center. Draw the centers first by drawing 5
points with 3 mm spacing between the points. Draw the circles the same size as the circles
in set 1, making the smallest circle on the right, and each successively large circle to the
left of the first circle. Indicate verbally that the centers represent a sound source that is
moving from left to right, and that circles are closer on the right side of the diagram. This
is a good time to point out the distinction between observation and inference. One can
observe that the lines are closer on the right side of the source. Ask the students what
they can infer about the frequency of the sound as observed by someone standing to the
right of the moving object, as well as the left of the moving object.
Draw set 3 in the same manner as set 2, but use a spacing of 6 mm between the centers.
What is observed about the wavelength? What can be inferred about the frequency from
observers on either left or right?
Draw set 4 in the same manner as sets 2 and 3, but use a spacing of 10 mm between the
centers, the same spacing as the circles. What is observed about the wavelength? What
can be inferred about the frequency from observers on either left or right?
Homework
Hewitt, Ch 25
p. 508 Check Concepts 1-20
Lab activity and authentic assessment
Students should demonstrate comprehension by verbally expressing the relationship between
motion of a sound source and the observed frequency of the sound. Also, they should demonstrate
comprehension of the effect of the location of the observer relative to the sound source. If time
permits, each group can present a summary of their findings to the class. Otherwise, the teacher
can circulate around the room and prompt members of each group to express the “big idea” of the
lesson, which is that motion of the sound source affects the frequency of the sound as observed by
a stationary observer.
Assessment
The student created diagram should be completed. See answer key for more information.
Debrief
A short discussion should follow the activity. Again, the goal is to have the students express the
“big idea” of the lesson without simply repeating words and formulas. The discussion should
conclude by drawing a connection between motion and frequency.
Modifications/Accommodations:
This is a good lab for making groups from students with varying English language abilities and
differing learning styles because the lab is very hands-on and uses common materials. Conceptual
relationships between relative motion, wavelength, frequency, and position of an observer.
Accommodations can be made for students with IEP’s by assisting them with setup and making
predictions.
Attachments:
Worksheet for student-created diagrams
Answer key for student-created diagrams
Doppler Effect with sound waves
Name:_______________________per:_________date:_____________
Describing sound from a stationary source
1. Draw set 1 with 5 concentric circles, each nested inside each other. Use equal spacing between
the circles, each one 5 mm apart. Make multiple drawings as space allows for practice. This pattern
represents sound waves coming from a static source.
2. What do the circles represent?
3. What does the distance between the circles represent?
4. Is this distance the same on all parts of the diagram?
Describing sound from a moving source
5. Draw set 2 with 5 circles, all with a different center. Draw the centers first by drawing 5 points
with 1 mm spacing between the points. Draw the circles the same size as the circles in set 1,
making the smallest circle on the right, and each successively large circle to the left of the first
circle.
6. If the center represents a moving sound source, in which direction is the sound source moving?
7. What can you observe about lines on the right side of the source?
8. What can you infer about the frequency of the sound as observed by someone standing to the
right of the moving object?
9. What can you infer about the frequency of the sound as observed by someone standing to the
right of the moving object?
10. Draw set 3 in the same manner as set 2, but use a spacing of 3 mm between the centers.
11. What can you observe about the wavelength on different parts of the diagram?
12. What can be inferred about the frequency by an observer on the left?
13. If an observer were standing in the center of the diagram, such that the object first
approaches and then recedes, what could be inferred about how the frequencies would be
observed?
14. Draw set 4 in the same manner as sets 2 and 3, but use a spacing of 5 mm between the
centers, the same spacing as the circles.
15. What is observed about the wavelength in this diagram?
16. What can be inferred about the frequency that would be observed on the left?
17. What can be inferred about the frequency from observers on the right?
18. What can be inferred about effect of the relatively dense grouping of sound waves on an
observer?
Doppler Effect with sound waves
Name:________________Key___________per:_________
Describing sound from a stationary source
1. Draw set 1 with 5 concentric circles, nested inside each other. Use equal spacing between the
circles, each one 5 mm apart. This pattern represents sound waves coming from a static source.
2. What do the circles represent?
Peaks of waveforms (sound compressions)
3. What does the distance between the circles represent?
One wavelength
4. Is this distance the same on all parts of the diagram?
Yes
5. Draw set 2 with 5 circles, all with a different center. Draw the centers first by drawing 5 points
with 1 mm spacing between the points. Draw the circles the same size as the circles in set 1,
making the smallest circle on the right, and each successively large circle to the left of the first
circle.
6. If the center represents a moving sound source, in which direction is the sound source moving?
Motion is from left to right
7. What can you observe about lines on the right side of the source?
They are relatively closely spaced
8. What can you infer about the frequency of the sound as observed by someone standing to the
right of the moving object?
The frequency will be higher
9. What can you infer about the frequency of the sound as observed by someone standing to the
left of the moving object?
The frequency will be lower
10. Draw set 3 in the same manner as set 2, but use a spacing of 3 mm between the centers.
11. What can you observe about the wavelength on different parts of the diagram?
The wavelength is even shorter on the right side, and even longer on the left.
12. What can be inferred about the frequency from observers on either the left or right?
The frequency is even higher on the right side, and even lower on the left.
13. If an observer were standing in the center of the diagram, such that the object first
approaches and then recedes, what could be inferred about how the frequencies would be
observed?
The frequency would decrease as the object passes the observer.
14. Draw set 4 in the same manner as sets 2 and 3, but use a spacing of 5 mm between the
centers, the same spacing as the circles.
15. What is observed about the wavelength in this diagram?
The wavelengths would be very small on the leading edge, forming one large wave (shock
wave).
16. What can be inferred about the frequency that would be observed on the left?
The frequency would be very low.
17. What can be inferred about the frequency from observers on the right?
The frequency would be very high.
18. What can be inferred about effect of the relatively dense grouping of sound waves on an
observer?
The sound would be very loud, as the waves would reach an observer all at once.