Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Cutnell/Johnson
Physics
Classroom Response System Questions
Chapter 17 The Principle of Linear
Superposition and Interference Phenomena
Interactive Lecture Questions
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17.1.1. The graph shows two waves at time t = 0 s, one moving toward
the right at 2.0 cm/s and the other moving toward the left at 2.0
cm/s. What will the amplitude be at x = 0 at time t = 0.5 s?
a) +1 cm
b) zero cm
c) -1 cm
d) -1.5 cm
e) -2.5 cm
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17.1.2. Two waves are traveling along a string. The graph shows the position
of the waves at time t = 0.0 s. One wave with a maximum amplitude of
0.5 cm is traveling toward the right at 0.5 cm/s. The second wave with a
maximum amplitude of 2.0 cm is traveling toward the left at 2.0 cm/s.
At what elapsed time will the two waves completely overlap and what
will the maximum amplitude be at that time?
a) 2.0 s, 1.5 cm
b) 1.6 s, 2.5 cm
c) 1.0 s, 1.5 cm
d) 1.0 s, 2.5 cm
e) 1.6 s, 1.5 cm
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17.1.3. Which one of the following waves would
undergo fully destructive interference with a wave
described by y = 2.0 sin (3.0x - 0.5t) where y and x
are measured in meters and t is measured in seconds?
a) y = -2.0 sin (3.0x - 0.5t)
b) y = 2.0 sin (3.0x + 0.5t))
c) y = 2.0 sin (-3.0x - 0.5t))
d) y = 2.0 sin (0.33x - 2.0t)
e) None of these equations will fully interfere
destructively with the given wave.
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17.1.4. Which one of the following waves would
undergo fully constructive interference with a wave
described by y = 2.0 sin (3.0x - 2.0t) where y and x
are measured in meters and t is measured in seconds?
a) y = sin (0.33x - 0.5t)
b) y = - sin (-3.0x + 2.0t)
c) y = - sin (-1.5x - t))
d) y = sin (x + 2t/3)
e) None of these equations will fully interfere
constructively with the given wave.
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Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
17.2.1. A radio station has a transmitting tower that transmits its signal (electromagnetic waves)
uniformly in all directions on the west end of Main Street. They are considering building a
second, identical transmitter at the east end of Main Street, ten miles due east of the first
transmitter. The same signal is to be broadcast at the same time from both towers. As you
drive ten miles east to west on Main Street, what would you hear as you listen to the radio
station broadcast from these two towers?
a) The signal gets stronger as you drive the first five miles, but then the signal decreases as you
travel the final five miles.
b) The signal is somewhat stronger than when there was just one tower and there is no variation
in signal strength as you drive the ten miles.
c) The signal alternates between increasing strength and decreasing strength as you drive the ten
miles.
d) The signal is the same as it was with just one tower. For the first five miles, you receive the
signal from the east tower. For the second five miles, you receive the signal from the west
tower.
e) To answer this question, one must know the amplitude of the broadcast signal.
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Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
17.2.2. A tuning fork, like the one shown in the drawing, is tapped and
begins to vibrate. When you place it next to you ear as shown, you can
hear a distinctive tone. The dashed lines in the picture indicate possible
axes of rotation. Consider each of the five axes shown. About which of
these axes can you rotate the tuning fork without producing some
constructive or destructive interference at the ear as it is rotated?
a) A only
b) B only
c) C only
d) D only
e) D and E only
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17.2.3. Two identical speakers are emitting a constant tone that has a
wavelength of 0.50 m. Speaker A is located to the left of speaker
B. At which of the following locations between the speakers
would complete destructive interference occur?
a) 2.15 m from speaker A and 3.00 m from speaker B
b) 3.75 m from speaker A and 2.50 m from speaker B
c) 2.50 m from speaker A and 1.00 m from speaker B
d) 1.35 m from speaker A and 3.75 m from speaker B
e) 2.00 m from speaker A and 3.00 m from speaker B
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17.3.1. A speaker is located inside a box and emits a constant tone. There is a partition in the box
that has a circular opening with the diameter shown. There is only one opening in the box to
the outside. That opening is also circular with the diameter shown. A man is slowly walking
alongside the box in the direction shown. What does the person hear, if anything, as he passes
the outer circular opening? Notes: Not all of the waves are shown and the walls do not absorb
any sound.
a) As the man walks along side the box,
he hears the constant tone emitted by the
speaker and its intensity increases as he
is passing the circular opening.
b) As the man walks along side the box,
he only hears the constant tone emitted
by the speaker when he is front of the
circular opening.
c) At no time does the man hear any
sound from the speaker.
d) As the man walks along side the box, he hears the tone intensity alternating between its
maximum and minimum values.
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17.3.2. Consider the situation shown below. You are walking north on
a street approaching a small marching band that is traveling west
to east. The large, shaded rectangles in the drawing represent tall
buildings. At the moment shown, which instrument(s) do you hear
first?
a) flute (f)
b) snare drum (sd)
c) bass drum (bd)
d) flute (f) and
snare drum (sd)
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17.4.1. Two waves, A and B, are superposed. For which one of the
following circumstances will beats result?
a) A and B are identical waves traveling in the same direction.
b) A and B are traveling with differing speeds.
c) A and B are identical waves traveling in the opposite directions.
d) A and B are waves with slightly differing frequencies, but
otherwise identical.
e) A and B are waves with slightly differing amplitudes, but otherwise
identical.
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17.4.2. Which of the graphs shown represent the superposition of two
different waves with the smaller difference in frequency between
the two waves?
a) A
b) B
c) both A and B, since
the frequency difference
is the same in the two cases
d) This cannot be answered
since no frequency information is available.
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17.4.3. Consider the following graphs,
each showing the resulting wave from
addition of two differing waves. For
which graph is the frequency
difference between the two original
waves the smallest?
a) 1
b) 2
c) 3
d) The frequency difference is the same
for graphs 1 and 3 and is the smallest.
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17.5.1. A transverse standing waves is present on a plucked guitar
string. What is the distance from the fixed end of a string to the
nearest antinode?
a) λ/4
b) λ/2
c) 2λ/3
d) 3λ/4
e) λ
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17.5.2. Which one of the following statements is true concerning the
points on a string that sustain a standing wave?
a) All points undergo motion that is purely longitudinal.
b) All points vibrate with the same energy.
c) All points vibrate with different amplitudes.
d) All points undergo the same displacements.
e) All points vibrate with different frequencies.
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17.5.3. A rope of length L is clamped at both ends. Which one of the
following is not a possible wavelength for standing waves on this
rope?
a) L/2
b) 2L/3
c) L
d) 2L
e) 4L
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17.5.4. Consider a wire under tension that is driven by an oscillator. Initially, the
wire is vibrating in its second harmonic mode. How does the oscillation of the
wire change as the frequency is slowly increased?
a) No standing wave may be observed until the frequency matches the third
harmonic mode of the wire.
b) No standing wave may be observed until the frequency matches the first
harmonic mode of the wire.
c) The observed oscillation of the wire not change until the frequency matches the
third harmonic mode of the wire.
d) The observed oscillation of the wire will slowly change in fractions of the
harmonic between the second and third harmonic modes.
e) The observed oscillation of the wire will slowly change in fractions of the
harmonic between the second and first harmonic modes.
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17.5.5. Which one of the following statements explains why a piano
and a guitar playing the same musical note sound different?
a) The fundamental frequency is different for each instrument.
b) The two instruments have the same fundamental frequency, but
different harmonic frequencies.
c) The two instruments have the same harmonic frequencies, but
different fundamental frequencies.
d) The two instruments have the same fundamental frequency and the
same harmonic frequencies, but the amounts of each of the
harmonics is different for the two instruments..
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17.5.6. The sound emitted from a strummed guitar string is either a
resonant frequency or one of its harmonics. Although the string
is not being driven at its resonant frequency, no non-resonant
waves are emitted. Which one of the following statements best
describes why non-resonant waves are not heard?
a) Non-resonant waves are not sound waves.
b) The non-resonant waves are too quickly damped out.
c) The musician has tuned the strings so that only resonant waves
will occur.
d) All non-resonant waves will destructively interfere with each
other.
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17.6.1. A soft drink bottle is 15 cm tall. Joey blows across that top
of the bottle just after drinking the last of his drink. What is the
approximate fundamental frequency of the tone that Joey
generates?
a) 230 Hz
b) 570 Hz
c) 680 Hz
d) 810 Hz
e) 1100 Hz
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17.6.2. An aluminum rod of length L may be held at various points
along its length, some of which are indicated in the drawing. A
small hammer is then used to tap the rod. As a result,
longitudinal standing waves are generated in the rod. At which
position should the rod be held to generate its second harmonic?
a) A
b) B
c) C
d) D
e) E
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17.6.3. Which one of the following statements concerning standing waves within a
pipe open only at one end is true?
a) The standing waves have a fundamental mode have a shorter wavelength than
that for the same tube with both ends open.
b) The standing waves must be transverse waves, since longitudinal waves could not
exit the tube.
c) The standing waves have a greater number of harmonics than which occur for the
tube when both ends are open.
d) The standing waves have fewer harmonics than which occur for the tube when
both ends are open.
e) The standing waves have a fundamental mode with a lower frequency than that
which occurs when both ends of the tube are open.
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17.6.4. Given that the first three resonant frequencies of an organ
pipe are 200, 600, and 1000 Hz, what can you conclude about
the pipe?
a) The pipe is open at both ends and has a length of 0.95 m.
b) The pipe is closed at one end and has a length of 0.95 m.
c) The pipe is closed at one end and has a length of 0.475 m.
d) The pipe is open at both ends and has a length of 0.475 m.
e) It is not possible to have a pipe with this combination of
resonant frequencies.
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