1. Halliday/Resnick/Walker Fundamentals of Physics
Classroom Response System Questions
Chapter 17 Waves II
Interactive Lecture Questions

2. 17. 3. 1. You are observing a thunderstorm
You are observing a thunderstorm. In the distance, you see a flash of lightning. Five seconds later, you hear thunder. How far away was the lightning flash?
a) 1 mile (1.6 km)
b) 0.5 mile (0.8 km)
c) 2 miles (3.2 km)
d) mile (0.4 km)
e) 5 miles (8.0 km)

3. 17. 3. 1. You are observing a thunderstorm
You are observing a thunderstorm. In the distance, you see a flash of lightning. Five seconds later, you hear thunder. How far away was the lightning flash?
a) 1 mile (1.6 km)
b) 0.5 mile (0.8 km)
c) 2 miles (3.2 km)
d) mile (0.4 km)
e) 5 miles (8.0 km)

4. In a classroom demonstration, a physics professor breathes in a small amount of helium and begins to talk. The result is that the professor’s normally low, baritone voice sounds quite high pitched. Which one of the following statements best describes this phenomena?
a) The presence of helium changes the speed of sound in the air in the room, causing all sounds to have higher frequencies.
b) The professor played a trick on the class by tightening his vocal cords to produces higher frequencies in his throat and mouth than normal. The helium was only a distraction and had nothing to do with it.
c) The helium significantly alters the vocal chords causing the wavelength of the sounds generated to decrease and thus the frequencies increase.
d) The wavelength of the sound generated in the professor’s throat and mouth is only changed slightly, but since the speed of sound in helium is approximately 2.5 times larger than in air, therefore the frequencies generated are about 2.5 times higher.

5. In a classroom demonstration, a physics professor breathes in a small amount of helium and begins to talk. The result is that the professor’s normally low, baritone voice sounds quite high pitched. Which one of the following statements best describes this phenomena?
a) The presence of helium changes the speed of sound in the air in the room, causing all sounds to have higher frequencies.
b) The professor played a trick on the class by tightening his vocal cords to produces higher frequencies in his throat and mouth than normal. The helium was only a distraction and had nothing to do with it.
c) The helium significantly alters the vocal chords causing the wavelength of the sounds generated to decrease and thus the frequencies increase.
d) The wavelength of the sound generated in the professor’s throat and mouth is only changed slightly, but since the speed of sound in helium is approximately 2.5 times larger than in air, therefore the frequencies generated are about 2.5 times higher.

6. The graph shows measured data for the speed of sound in water and the density of the water versus temperature. From the graph and your knowledge of the speed of sound in liquids, what can we infer about the bulk modulus of water in the temperature range from 0 to 100 C?
a) The bulk modulus of
water increases linearly
with temperature.
b) The bulk modulus of
water decreases non-linearly
c) The bulk modulus of
water is constant with
increasing temperature.
d) The bulk modulus of
water increases non-linearly
with increasing temperature.
e) The bulk modulus of
water increases with
increasing temperature until it
peaks around 60 C after which it slowly decreases.

7. The graph shows measured data for the speed of sound in water and the density of the water versus temperature. From the graph and your knowledge of the speed of sound in liquids, what can we infer about the bulk modulus of water in the temperature range from 0 to 100 C?
a) The bulk modulus of
water increases linearly
with temperature.
b) The bulk modulus of
water decreases non-linearly
c) The bulk modulus of
water is constant with
increasing temperature.
d) The bulk modulus of
water increases non-linearly
with increasing temperature.
e) The bulk modulus of
water increases with
increasing temperature until it
peaks around 60 C after which it slowly decreases.

8. 17. 3. 4. A stationary railroad whistle is sounded. An echo is heard 5
A stationary railroad whistle is sounded. An echo is heard 5.0 seconds later by the train’s engineer. If the speed of sound is 343 m/s, how far away is the reflecting surface?
a) 68 m
b) 140 m
c) 860 m
d) m
e) m

9. 17. 3. 4. A stationary railroad whistle is sounded. An echo is heard 5
A stationary railroad whistle is sounded. An echo is heard 5.0 seconds later by the train’s engineer. If the speed of sound is 343 m/s, how far away is the reflecting surface?
a) 68 m
b) 140 m
c) 860 m
d) m
e) m

10. Two fans are watching a baseball game from different positions. One fan is located directly behind home plate, 18.3 m from the batter. The other fan is located in the centerfield bleachers, 127 m from the batter. Both fans observe the batter strike the ball at the same time (because the speed of light is about a million times faster than that of sound), but the fan behind home plate hears the sound first. What is the time difference between hearing the sound at the two locations? Use 345 m/s as the speed of sound.
a) s
b) s
c) s
d) s
e) s

11. Two fans are watching a baseball game from different positions. One fan is located directly behind home plate, 18.3 m from the batter. The other fan is located in the centerfield bleachers, 127 m from the batter. Both fans observe the batter strike the ball at the same time (because the speed of light is about a million times faster than that of sound), but the fan behind home plate hears the sound first. What is the time difference between hearing the sound at the two locations? Use 345 m/s as the speed of sound.
a) s
b) s
c) s
d) s
e) s

12. 17. 3. 6. Ethanol has a density of 659 kg/m3
Ethanol has a density of 659 kg/m3. If the speed of sound in ethanol is 1162 m/s, what is its adiabatic bulk modulus?
a) 1.7  108 N/m2
b) 2.2  108 N/m2
c) 7.7  108 N/m2
d) 8.9  108 N/m2
e) 6.1  109 N/m2

13. 17. 3. 6. Ethanol has a density of 659 kg/m3
Ethanol has a density of 659 kg/m3. If the speed of sound in ethanol is 1162 m/s, what is its adiabatic bulk modulus?
a) 1.7  108 N/m2
b) 2.2  108 N/m2
c) 7.7  108 N/m2
d) 8.9  108 N/m2
e) 6.1  109 N/m2

14. The speaker and two microphones shown in the figure are arranged inside a sealed container filled with neon gas. The wires from the microphones are connected to an oscilloscope (not shown). The signal from the microphones is monitored beginning at time t = 0 s when a sound pulse is emitted from the speaker. The pulse is picked up by microphone 1 at t1 = × 10–2 s and by microphone 2 at t2 = × 10–2 s. What is the speed of sound in neon gas?
a) 724 m/s
b) 362 m/s
c) 124 m/s
d) 174 m/s
e) 435 m/s

15. The speaker and two microphones shown in the figure are arranged inside a sealed container filled with neon gas. The wires from the microphones are connected to an oscilloscope (not shown). The signal from the microphones is monitored beginning at time t = 0 s when a sound pulse is emitted from the speaker. The pulse is picked up by microphone 1 at t1 = × 10–2 s and by microphone 2 at t2 = × 10–2 s. What is the speed of sound in neon gas?
a) 724 m/s
b) 362 m/s
c) 124 m/s
d) 174 m/s
e) 435 m/s

16. A particle of dust is floating in the air approximately one half meter in front of a speaker. The speaker is then turned on produces a constant pure tone of 226 Hz, as shown. The sound waves produced by the speaker travel horizontally. Which one of the following statements correctly describes the subsequent motion of the dust particle, if any?
a) The particle of dust will oscillate left and right with a frequency of 226 Hz.
b) The particle of dust will oscillate up and down with a frequency of 226 Hz.
c) The particle of dust will be accelerated toward the right and continue moving in that direction.
d) The particle of dust will move toward the right at constant velocity.
e) The dust particle will remain motionless as it cannot be affected by sound waves.

17. A particle of dust is floating in the air approximately one half meter in front of a speaker. The speaker is then turned on produces a constant pure tone of 226 Hz, as shown. The sound waves produced by the speaker travel horizontally. Which one of the following statements correctly describes the subsequent motion of the dust particle, if any?
a) The particle of dust will oscillate left and right with a frequency of 226 Hz.
b) The particle of dust will oscillate up and down with a frequency of 226 Hz.
c) The particle of dust will be accelerated toward the right and continue moving in that direction.
d) The particle of dust will move toward the right at constant velocity.
e) The dust particle will remain motionless as it cannot be affected by sound waves.

18. 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 would complete destructive interference occur?
a) m from speaker A and 3.00 m from speaker B
b) m from speaker A and 2.50 m from speaker B
c) m from speaker A and 1.00 m from speaker B
d) m from speaker A and 3.75 m from speaker B
e) m from speaker A and 3.00 m from speaker B

19. 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 would complete destructive interference occur?
a) m from speaker A and 3.00 m from speaker B
b) m from speaker A and 2.50 m from speaker B
c) m from speaker A and 1.00 m from speaker B
d) m from speaker A and 3.75 m from speaker B
e) m from speaker A and 3.00 m from speaker B

20. 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.

21. 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.

22. A tuning fork, like the one shown in the drawing, is tapped and begins to vibrate. When you place it next to your ear as shown, you can hear a distinctive tone. The dashed lines in the picture indicate possible axes of rotation. Consider each if the five axes shown. About which of these axes can you rotate the tuning fork without producing 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

23. A tuning fork, like the one shown in the drawing, is tapped and begins to vibrate. When you place it next to your ear as shown, you can hear a distinctive tone. The dashed lines in the picture indicate possible axes of rotation. Consider each if the five axes shown. About which of these axes can you rotate the tuning fork without producing 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

24. Natalie is a distance d in front of a speaker emitting sound waves. She then moves to a position that is a distance 2d in front of the speaker. By what percentage does the sound intensity decrease for Natalie between the two positions?
a) 10 %
b) 25 %
c) 50 %
d) 75%
e) The sound intensity remains constant because it is not dependent on the distance.

25. Natalie is a distance d in front of a speaker emitting sound waves. She then moves to a position that is a distance 2d in front of the speaker. By what percentage does the sound intensity decrease for Natalie between the two positions?
a) 10 %
b) 25 %
c) 50 %
d) 75%
e) The sound intensity remains constant because it is not dependent on the distance.

26. A bell is ringing inside of a sealed glass jar that is connected to a vacuum pump. Initially, the jar is filled with air at atmospheric pressure. What does one hear as the air is slowly removed from the jar by the pump?
a) The sound intensity gradually increases.
b) The sound intensity gradually decreases.
c) The sound intensity of the bell does not change.
d) The frequency of the sound gradually increases.
e) The frequency of the sound gradually decreases.

27. A bell is ringing inside of a sealed glass jar that is connected to a vacuum pump. Initially, the jar is filled with air at atmospheric pressure. What does one hear as the air is slowly removed from the jar by the pump?
a) The sound intensity gradually increases.
b) The sound intensity gradually decreases.
c) The sound intensity of the bell does not change.
d) The frequency of the sound gradually increases.
e) The frequency of the sound gradually decreases.

28. A sound level meter is used measure the sound intensity level. A sound level meter is placed an equal distance in front of two speakers, one to the left and one to the right. A signal of constant frequency may be sent to each of the speakers independently or at the same time. When either the left speaker is turned on or the right speaker is turned on, the sound level meter reads 90.0 dB. What will the sound level meter read when both speakers are turned on at the same time?
a) dB
b) dB
c) dB
d) dB
e) dB

29. A sound level meter is used measure the sound intensity level. A sound level meter is placed an equal distance in front of two speakers, one to the left and one to the right. A signal of constant frequency may be sent to each of the speakers independently or at the same time. When either the left speaker is turned on or the right speaker is turned on, the sound level meter reads 90.0 dB. What will the sound level meter read when both speakers are turned on at the same time?
a) dB
b) dB
c) dB
d) dB
e) dB

30. A sound level meter is used measure the sound intensity level. A sound level meter is placed an equal distance in front of two speakers, one to the left and one to the right. A signal of constant frequency, but differing amplitude, is sent to each speaker independently. When the left speaker is turned on the sound level meter reads 85 dB. When the right speaker is turned on the sound level meter reads 65 dB. What will the sound level meter read when both speakers are turned on at the same time?
a) about 85 dB
b) about 65 dB
c) about 150 dB
d) about 75 dB
e) about 113 dB

31. A sound level meter is used measure the sound intensity level. A sound level meter is placed an equal distance in front of two speakers, one to the left and one to the right. A signal of constant frequency, but differing amplitude, is sent to each speaker independently. When the left speaker is turned on the sound level meter reads 85 dB. When the right speaker is turned on the sound level meter reads 65 dB. What will the sound level meter read when both speakers are turned on at the same time?
a) about 85 dB
b) about 65 dB
c) about 150 dB
d) about 75 dB
e) about 113 dB

32. During a typical workday (eight hours), the average sound intensity arriving at Larry’s ear is 1.8  10–5 W/m2. If the area of Larry’s ear through which the sound passes is 2.1  10–3 m2, what is the total energy entering each of Larry’s ears during the workday?
a) 1.8  10–5 J
b) 1.1  10–3 J
c) 7.4  10–4 J
d) 4.1  10–3 J
e) 2.2  10–4 J

33. During a typical workday (eight hours), the average sound intensity arriving at Larry’s ear is 1.8  10–5 W/m2. If the area of Larry’s ear through which the sound passes is 2.1  10–3 m2, what is the total energy entering each of Larry’s ears during the workday?
a) 1.8  10–5 J
b) 1.1  10–3 J
c) 7.4  10–4 J
d) 4.1  10–3 J
e) 2.2  10–4 J

34. 17. 6. 6. Two boys are whispering in the library
Two boys are whispering in the library. The radiated sound power from one boy’s mouth is 1.2 × 10–9 W; and it spreads out uniformly in all directions. What is the minimum distance the boys must be away from the librarian so that she will not be able to hear them? The threshold of hearing for the librarian is 1.00 × 10–12 W/m2.
a) 9.8 m
b) 16 m
c) 23 m
d) 35 m
e) 100 m

35. 17. 6. 6. Two boys are whispering in the library
Two boys are whispering in the library. The radiated sound power from one boy’s mouth is 1.2 × 10–9 W; and it spreads out uniformly in all directions. What is the minimum distance the boys must be away from the librarian so that she will not be able to hear them? The threshold of hearing for the librarian is 1.00 × 10–12 W/m2.
a) 9.8 m
b) 16 m
c) 23 m
d) 35 m
e) 100 m

36. According to US government regulations, the maximum sound intensity level in the workplace is 90.0 dB. Within one factory, 32 identical machines produce a sound intensity level of 92.0 dB. How many machines must be removed to bring the factory into compliance with the regulation?
a) 2
b) 8
c) 12
d) 16
e) 24

37. According to US government regulations, the maximum sound intensity level in the workplace is 90.0 dB. Within one factory, 32 identical machines produce a sound intensity level of 92.0 dB. How many machines must be removed to bring the factory into compliance with the regulation?
a) 2
b) 8
c) 12
d) 16
e) 24

38. Software is used to amplify a digital sound file on a computer by 20 dB. By what factor has the intensity of the sound been increased as compared to the original sound file?
a) 2
b) 5
c) 10
d) 20
e) 100

39. Software is used to amplify a digital sound file on a computer by 20 dB. By what factor has the intensity of the sound been increased as compared to the original sound file?
a) 2
b) 5
c) 10
d) 20
e) 100

40. 17. 7. 1. A girl is playing a trumpet
A girl is playing a trumpet. The sound waves produced are traveling through air to your ear. Which one of the following statements is false concerning this situation?
a) A high-frequency sound that the trumpet produces is interpreted as a high-pitched sound.
b) Air molecules between the trumpet and your ear vibrate back and forth parallel to the direction the waves are traveling.
c) The loudness of the sound wave involves the size of the oscillations in air pressure.
d) The sounds from the trumpet are longitudinal waves.
e) The sound travels at the speed of light to your ear.

41. 17. 7. 1. A girl is playing a trumpet
A girl is playing a trumpet. The sound waves produced are traveling through air to your ear. Which one of the following statements is false concerning this situation?
a) A high-frequency sound that the trumpet produces is interpreted as a high-pitched sound.
b) Air molecules between the trumpet and your ear vibrate back and forth parallel to the direction the waves are traveling.
c) The loudness of the sound wave involves the size of the oscillations in air pressure.
d) The sounds from the trumpet are longitudinal waves.
e) The sound travels at the speed of light to your ear.

42. While constructing a rail line in the 1800s, spikes were driven to attach the rails to cross ties with a sledge hammer. Consider the sound that is generated each time the hammer hits the spike. How does the frequency of the sound change, if at all, as the spike is driven into the tie?
a) The frequency of the sound does not change as the spike is driven.
b) The frequency of the sound decreases as the spike is driven.
c) The frequency of the sound increases as the spike is driven.

43. While constructing a rail line in the 1800s, spikes were driven to attach the rails to cross ties with a sledge hammer. Consider the sound that is generated each time the hammer hits the spike. How does the frequency of the sound change, if at all, as the spike is driven into the tie?
a) The frequency of the sound does not change as the spike is driven.
b) The frequency of the sound decreases as the spike is driven.
c) The frequency of the sound increases as the spike is driven.

44. 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) Any non-resonant waves will destructively interfere with each other.

45. 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) Any non-resonant waves will destructively interfere with each other.

46. 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 smaller frequency than that which occurs when both ends of the tube are open.

47. 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 smaller frequency than that which occurs when both ends of the tube are open.

48. 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 m.
d) The pipe is open at both ends and has a length of m.
e) It is not possible to have a pipe with this combination of resonant frequencies.

49. 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 m.
d) The pipe is open at both ends and has a length of m.
e) It is not possible to have a pipe with this combination of resonant frequencies.

50. 17. 7. 6. A soft drink bottle is 15 cm tall
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) Hz

51. 17. 7. 6. A soft drink bottle is 15 cm tall
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) Hz

52. 17.8.1. Consider the following graphs, each
showing the result waves 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.

53. 17.8.1. Consider the following graphs, each
showing the result waves 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.

54. 17. 8. 2. Two waves, A and B, are superposed
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.

55. 17. 8. 2. Two waves, A and B, are superposed
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.

56. Two stationary observers, Keisha and Trina, are listening to the sound from a moving source. The sound from the source has a constant frequency fS and constant amplitude. As the source moves, Trina hears two different frequencies f1 and f2, where f1 > fS and f2 < fS. Keisha, who is not moving with the source, only hears one frequency, f. Which one of the following statements best explains this situation?.
a) The source is moving very slowly relative to Keisha, but fast relative to Trina.
b) The source is moving along a parabolic path and Keisha is at the origin of the parabola. Trina is inside the parabola.
c) Keisha is standing at a location where the wind is blowing in such a way as to remove the Doppler effect, while Trina is standing in a location where there is no wind.
d) The source is moving along a circle and Keisha is at the center of the circle. Trina is outside the circle.
e) The source is moving along an ellipse and Keisha is at one of the two foci of the ellipse. Trina is outside the ellipse.

57. Two stationary observers, Keisha and Trina, are listening to the sound from a moving source. The sound from the source has a constant frequency fS and constant amplitude. As the source moves, Trina hears two different frequencies f1 and f2, where f1 > fS and f2 < fS. Keisha, who is not moving with the source, only hears one frequency, f. Which one of the following statements best explains this situation?.
a) The source is moving very slowly relative to Keisha, but fast relative to Trina.
b) The source is moving along a parabolic path and Keisha is at the origin of the parabola. Trina is inside the parabola.
c) Keisha is standing at a location where the wind is blowing in such a way as to remove the Doppler effect, while Trina is standing in a location where there is no wind.
d) The source is moving along a circle and Keisha is at the center of the circle. Trina is outside the circle.
e) The source is moving along an ellipse and Keisha is at one of the two foci of the ellipse. Trina is outside the ellipse.

58. A child is swinging back and forth with a constant period and amplitude. Somewhere in front of the child, a stationary horn is emitting a constant tone of frequency fS. Five points are labeled in the drawing to indicate positions along the arc as the child swings. At which position(s) will the child hear the lowest frequency for the sound from the whistle?
a) at B when moving toward A
b) at B when moving toward C
c) at C when moving toward B
d) at C when moving toward D
e) at both A and D

59. A child is swinging back and forth with a constant period and amplitude. Somewhere in front of the child, a stationary horn is emitting a constant tone of frequency fS. Five points are labeled in the drawing to indicate positions along the arc as the child swings. At which position(s) will the child hear the lowest frequency for the sound from the whistle?
a) at B when moving toward A
b) at B when moving toward C
c) at C when moving toward B
d) at C when moving toward D
e) at both A and D

60. Hydrogen atoms in a distant galaxy are observed to emit light that is shifted to lower frequencies with respect to hydrogen atoms here on Earth. Astronomers use this information to determine the relative velocity of the galaxy with respect to the Earth by observing how light emitted by atoms is Doppler shifted. For the hydrogen atoms mentioned, how are the wavelengths of light affected by the relative motion, if at all?
a) The wavelengths would be unchanged, only the frequencies are shifted.
b) The wavelengths of light would be longer than those observed on Earth.
c) The wavelengths of light would be shorter than those observed on Earth.

61. Hydrogen atoms in a distant galaxy are observed to emit light that is shifted to lower frequencies with respect to hydrogen atoms here on Earth. Astronomers use this information to determine the relative velocity of the galaxy with respect to the Earth by observing how light emitted by atoms is Doppler shifted. For the hydrogen atoms mentioned, how are the wavelengths of light affected by the relative motion, if at all?
a) The wavelengths would be unchanged, only the frequencies are shifted.
b) The wavelengths of light would be longer than those observed on Earth.
c) The wavelengths of light would be shorter than those observed on Earth.