Quiz on Waves and Sound
1. The frequencies of the first two overtones (second and third harmonics) of a vibrating string
are f and 3f/2 .What is the fundamental frequency of this string?
A) f/3 B) f/2 C) f D) 2f
A standing wave of frequency 5 hertz is set up on a string 2 meters long with nodes at both ends and in
the center, as shown above.
2. The speed at which waves propagate on the string is
A) 0.4 m/s
B) 2.5 m/s
C) 5 m/s
D) 10 m/s
3. The fundamental frequency of vibration of the string is
A) 1 Hz
B) 2.5 Hz
C) 5 Hz
D) 10 Hz
4. If the frequency of sound wave is doubled, the wavelength:
A) halves and the speed remains unchanged.
B) doubles and the speed remains unchanged.
C) halves and the speed halves.
D) doubles and the speed doubles.
5. If the speed of sound in air is 340 m/s, the length of the organ pipe, open at both ends, that can
resonate at the fundamental frequency of 136 Hz, would be:
A) 0.40 m
B) 0.80 m
C) 1.25 m
D) 2.5 m
6. As sound travels from steel into air, both its speed and its:
A) wavelength increase
B) wavelength decrease
C) frequency increase
D) frequency remain unchanged
For Questions 7-8: The graph below was produced by a microphone in front of a tuning fork. It shows the
voltage produced from the microphone as a function of time.
7. The frequency of the tuning fork is (approximately)
A) 0.004 s
B) 0.020 s
C) 50Hz
D) 250 Hz
8. In order to calculate the speed of sound from the graph, you would also need to know
A) pitch
B) wavelength
C) frequency
D) volume
9. For a standing wave mode on a string fixed at both ends, adjacent antinodes are separated by a
distance of 20 cm. Waves travel on this string at a speed of 1200 cm/s. At what frequency is the string
vibrated to produce this standing wave?
(A) 120 Hz
(B) 60 Hz
(C) 40 Hz
(D) 30 Hz
10. A vibrating tuning fork sends sound waves into the air surrounding it. During the time in which the
tuning fork makes one complete vibration, the emitted wave travels
(A) one wavelength
(B) about 340 meters
(C) a distance directly proportional to the square root of the air density
(D) a distance inversely proportional to the square root of the pressure
11. Two wave pulses, each of wavelength λ, are
traveling toward each other along a rope as
shown. When both pulses are in the region
between points X and Y, which are a distance λ
apart, the shape of the rope is
A.
C.
B.
D.
12. Multiple Correct: Two fire trucks have sirens that emit waves of the same frequency. As the fire
trucks approach a person, the person hears a higher frequency from truck X than from truck Y. Which of
the following statements about truck X can be correctly inferred from this information? Select two
answers.
A) It is traveling faster than truck Y.
B) It is closer to the person than truck Y.
C) It is speeding up, and truck Y is slowing down.
D) Its wavefronts are closer together than truck Y.
13. Assume that waves are propagating in a uniform medium. If the frequency of the wave source
doubles then
A) the wavelength of the waves halves. B) the wavelength of the waves doubles.
C) the speed of the waves halves.
D) the speed of the waves doubles
For Questions 14-15: The figure above shows a transverse wave traveling to the right at a
particular instant of time. The period of the wave is 0.2 s.
14. What is the amplitude of the wave?
A) 4 cm
B) 5 cm
C) 8 cm
15. What is the speed of the wave?
A) 4 cm/s
B) 25 cm/s
C) 50 cm/s
D) 10 cm
D) 100 cm/s
16. The figure above shows two wave pulses that are approaching each other. Which of the following
best shows the shape of the resultant pulse when the centers of the pulses, points P and Q coincide?
A.
B.
C.
D.
17. Assume the speed of sound is 340 m/s. One stereo loudspeaker produces a sound with a wavelength
of 0.68 meters while the other speaker produces sound with a wavelength of 0.65 m. What would be the
resulting beat frequency?
A) 3 Hz
B) 23 Hz
C) 511.5 Hz
D) 11,333 Hz
18. Seven seconds after a brilliant flash of lightning, thunder shakes the house. Approximately how far
was the lightning strike from the house?
A) much closer than one kilometer
B) about one kilometer away
C) about two kilometers away
D) much farther away than two kilometers
E) It is impossible to say.
19. You double your distance from a sound source that is radiating equally in all directions. What
happens to the intensity of the sound? It reduces to
A) one-half its original value.
B) one-fourth its original value.
C) one-sixteenth its original value.
D) none of the above
20. Two tuning forks have frequencies of 440 and 522 Hz. What is the beat frequency if both are
sounding simultaneously?
A) 962 Hz
B) 481 Hz
C) 82 Hz
D) 55 Hz
E) 41 Hz
Show your work or explain your answer.
1. To demonstrate standing waves, one end of a string is attached to a tuning fork with frequency
120 Hz. The other end of the string passes over a pulley and is connected to a suspended mass
M as shown in the figure above. The value of M is such that the standing wave pattern has four
"loops." The length of the string from the tuning fork to the point where the string touches the top
of the pulley is 1.20 m. The linear density of the string is 1.0 x 10–4 kg/m, and remains constant
throughout the experiment.
a. Determine the wavelength of the standing wave.
b. Determine the speed of transverse waves along the string.
c. The speed of waves along the string increases with increasing tension in the string. Indicate whether
the value of M should be increased or decreased in order to double the number of loops in the standing
wave pattern. Justify your answer.
d. If a point on the string at an antinode moves a total vertical distance of 4 cm during one complete cycle,
what is the amplitude of the standing wave?
2.