Question 1

This graph shows the position of an element of air as a function of time as a sound wave passes through it. Which letter corresponds to the amplitude of the wave?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
E)  E 
A)  A 
B)  B 
C)  C 
D)  D 
E)  E D

Question 2

Which of the following properties of a sound wave determine its "pitch"?

Accepted Answer

A)  amplitude 
B)  distance form source to detector 
C)  frequency 
D)  phase 
E)  speed 
A)  amplitude 
B)  distance form source to detector 
C)  frequency 
D)  phase 
E)  speed C

Question 3

Beats in sound occur when:

Accepted Answer

A)  two waves of the same frequency interfere 
B)  two waves of slightly different frequency interfere 
C)  a reflected wave interferes with an incident wave 
D)  waves travel in two media having slightly different sound velocities 
E)  source and observer are in relative motion 
A)  two waves of the same frequency interfere 
B)  two waves of slightly different frequency interfere 
C)  a reflected wave interferes with an incident wave 
D)  waves travel in two media having slightly different sound velocities 
E)  source and observer are in relative motion B

Question 4

The lowest tone produced by a certain organ comes from a 3.0-m pipe with both ends open. If the speed of sound is 340 m/s, the frequency of this tone is approximately:

Accepted Answer

A)  14 Hz 
B)  28 Hz 
C)  57 Hz 
D)  110 Hz 
E)  230 Hz 
A)  14 Hz 
B)  28 Hz 
C)  57 Hz 
D)  110 Hz 
E)  230 Hz

Question 5

A source emits sound with a frequency of 1000 Hz. It and an observer are moving toward each other, each with a speed of 100 m/s. If the speed of sound is 340 m/s, the observer hears sound with a frequency of:

Accepted Answer

A)  290 Hz 
B)  540 Hz 
C)  1000 Hz 
D)  1800 Hz 
E)  3400 Hz 
A)  290 Hz 
B)  540 Hz 
C)  1000 Hz 
D)  1800 Hz 
E)  3400 Hz

Question 6

A stationary source S generates circular outgoing waves on a lake. The wave speed is 5.0 m/s and the crest-to-crest distance is 2.0 m. A person in a motor boat heads directly toward S at 3.0 m/s. To this person, the frequency of these waves is:

Accepted Answer

A)  1.0 Hz 
B)  1.5 Hz 
C)  2.0 Hz 
D)  4.0 Hz 
E)  8.0 Hz 
A)  1.0 Hz 
B)  1.5 Hz 
C)  2.0 Hz 
D)  4.0 Hz 
E)  8.0 Hz

Question 7

The sound level at a point P is 14 db below the sound level at a point 1.0 m from a point source. Assuming the intensity from a point source drops off like the inverse square of the distance, the distance from the source to point P is:

Accepted Answer

A)  4.0 cm 
B)  20 m 
C)  2.0 m 
D)  5.0 m 
E)  25 m 
A)  4.0 cm 
B)  20 m 
C)  2.0 m 
D)  5.0 m 
E)  25 m

Question 8

A 200-cm organ pipe with one end open is in resonance with a sound wave of wavelength 270 cm. The pipe is operating in its:

Accepted Answer

A)  fundamental frequency 
B)  first harmonic 
C)  second harmonic 
D)  third harmonic 
E)  fourth harmonic 
A)  fundamental frequency 
B)  first harmonic 
C)  second harmonic 
D)  third harmonic 
E)  fourth harmonic

Question 9

Two pipes are each open at one end and closed at the other. Pipe A has length L and pipe B has length 2L. Which harmonic of pipe B matches in frequency the fundamental of pipe A?

Accepted Answer

A)  The fundamental 
B)  The second 
C)  The third 
D)  The fourth 
E)  There are none 
A)  The fundamental 
B)  The second 
C)  The third 
D)  The fourth 
E)  There are none

Question 10

The speed of a sound wave is determined by:

Accepted Answer

A)  its amplitude 
B)  its intensity 
C)  its pitch 
D)  number of overtones present 
E)  the transmitting medium 
A)  its amplitude 
B)  its intensity 
C)  its pitch 
D)  number of overtones present 
E)  the transmitting medium

Question 11

Two waves are out of phase by half a wavelength. What is this in degrees?

Accepted Answer

A)  45° 
B)  90° 
C)  135° 
D)  180° 
E)  360° 
A)  45° 
B)  90° 
C)  135° 
D)  180° 
E)  360°

Question 12

The intensity of a certain sound wave is 6 $\mu$W/cm2. If its intensity is raised by 10 decibels, the new intensity is:

Accepted Answer

A)  60 $\mu$W/cm2 
B)  6.6 $\mu$W/cm2 
C)  6.06$\mu$W/cm2 
D)  600 $\mu$W/cm2 
E)  12 $\mu$W/cm2 
A)  60 $\mu$W/cm2 
B)  6.6 $\mu$W/cm2 
C)  6.06$\mu$W/cm2 
D)  600 $\mu$W/cm2 
E)  12 $\mu$W/cm2

Question 13

A microphone of surface area 2.0 cm2 absorbs 1.1 mW of sound. What is the intensity of sound hitting the microphone?

Accepted Answer

A)  2.2 x 10-5 W/m2  
B)  0.55 W/m2  
C)  2.2 W/m2 
D)  2.8 W/m2 
E)  5.5 W/m2 
A)  2.2 x 10-5 W/m2  
B)  0.55 W/m2  
C)  2.2 W/m2 
D)  2.8 W/m2 
E)  5.5 W/m2

Question 14

The rise in pitch of an approaching siren is an apparent increase in its:

Accepted Answer

A)  speed 
B)  amplitude 
C)  frequency 
D)  wavelength 
E)  number of overtones 
A)  speed 
B)  amplitude 
C)  frequency 
D)  wavelength 
E)  number of overtones

Question 15

A source emits sound with a frequency of 1000 Hz. It is moving at 20 m/s toward a stationary reflecting wall. If the speed of sound is 340 m/s an observer at rest directly behind the source hears a beat frequency of:

Accepted Answer

A)  3.0 Hz 
B)  55 Hz 
C)  63 Hz 
D)  114 Hz 
E)  118 Hz 
A)  3.0 Hz 
B)  55 Hz 
C)  63 Hz 
D)  114 Hz 
E)  118 Hz

Question 16

Organ pipe Y (open at both ends) is twice as long as organ pipe X (open at one end) as shown. The ratio of their fundamental frequencies fX::fY is:

Accepted Answer

A)  1:1 
B)  1:2 
C)  2:1 
D)  1:4 
E)  4:1 
A)  1:1 
B)  1:2 
C)  2:1 
D)  1:4 
E)  4:1

Question 17

A sound wave has a wavelength of 3.0 m. The distance from a compression center to the adjacent rarefaction center is:

Accepted Answer

A)  0.75 m 
B)  1.5 m 
C)  3.0 m 
D)  need to know wave speed 
E)  need to know frequency 
A)  0.75 m 
B)  1.5 m 
C)  3.0 m 
D)  need to know wave speed 
E)  need to know frequency

Question 18

Five organ pipes are described below. Which one has the highest fundamental frequency?

Accepted Answer

A)  A 2.3-m pipe with one end open and the other closed 
B)  A 3.3-m pipe with one end open and the other closed 
C)  A 1.6-m pipe with both ends open 
D)  A 3.0-m pipe with both ends open 
E)  a pipe in which the displacement nodes are 5 m apart 
A)  A 2.3-m pipe with one end open and the other closed 
B)  A 3.3-m pipe with one end open and the other closed 
C)  A 1.6-m pipe with both ends open 
D)  A 3.0-m pipe with both ends open 
E)  a pipe in which the displacement nodes are 5 m apart

Question 19

The valves of a trumpet and the slide of a trombone are for the purpose of:

Accepted Answer

A)  playing short (staccato) notes 
B)  tuning the instruments 
C)  changing the harmonic content 
D)  changing the length of the air column 
E)  producing gradations in loudness 
A)  playing short (staccato) notes 
B)  tuning the instruments 
C)  changing the harmonic content 
D)  changing the length of the air column 
E)  producing gradations in loudness

Question 20

To produce beats it is necessary to use two waves:

Accepted Answer

A)  traveling in opposite directions 
B)  of slightly different frequencies 
C)  of equal wavelengths 
D)  of equal amplitudes 
E)  whose ratio of frequencies is an integer 
A)  traveling in opposite directions 
B)  of slightly different frequencies 
C)  of equal wavelengths 
D)  of equal amplitudes 
E)  whose ratio of frequencies is an integer

Exam 17: Waves II

This graph shows the position of an element of air as a function of time as a sound wave passes through it. Which letter corresponds to the amplitude of the wave?

Which of the following properties of a sound wave determine its "pitch"?

Beats in sound occur when:

The lowest tone produced by a certain organ comes from a 3.0-m pipe with both ends open. If the speed of sound is 340 m/s, the frequency of this tone is approximately:

A source emits sound with a frequency of 1000 Hz. It and an observer are moving toward each other, each with a speed of 100 m/s. If the speed of sound is 340 m/s, the observer hears sound with a frequency of:

A stationary source S generates circular outgoing waves on a lake. The wave speed is 5.0 m/s and the crest-to-crest distance is 2.0 m. A person in a motor boat heads directly toward S at 3.0 m/s. To this person, the frequency of these waves is:

The sound level at a point P is 14 db below the sound level at a point 1.0 m from a point source. Assuming the intensity from a point source drops off like the inverse square of the distance, the distance from the source to point P is:

A 200-cm organ pipe with one end open is in resonance with a sound wave of wavelength 270 cm. The pipe is operating in its:

Two pipes are each open at one end and closed at the other. Pipe A has length L and pipe B has length 2L. Which harmonic of pipe B matches in frequency the fundamental of pipe A?

The speed of a sound wave is determined by:

Two waves are out of phase by half a wavelength. What is this in degrees?

The intensity of a certain sound wave is 6 μ\muμ W/cm2. If its intensity is raised by 10 decibels, the new intensity is:

A microphone of surface area 2.0 cm2 absorbs 1.1 mW of sound. What is the intensity of sound hitting the microphone?

The rise in pitch of an approaching siren is an apparent increase in its:

A source emits sound with a frequency of 1000 Hz. It is moving at 20 m/s toward a stationary reflecting wall. If the speed of sound is 340 m/s an observer at rest directly behind the source hears a beat frequency of:

Organ pipe Y (open at both ends) is twice as long as organ pipe X (open at one end) as shown. The ratio of their fundamental frequencies fX::fY is:

A sound wave has a wavelength of 3.0 m. The distance from a compression center to the adjacent rarefaction center is:

Five organ pipes are described below. Which one has the highest fundamental frequency?

The valves of a trumpet and the slide of a trombone are for the purpose of:

To produce beats it is necessary to use two waves:

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The intensity of a certain sound wave is 6 $\mu$ W/cm². If its intensity is raised by 10 decibels, the new intensity is:

A microphone of surface area 2.0 cm² absorbs 1.1 mW of sound. What is the intensity of sound hitting the microphone?

Organ pipe Y (open at both ends) is twice as long as organ pipe X (open at one end) as shown. The ratio of their fundamental frequencies f_X::f_Y is: