Question 1

The speed of sound in air is 340 m/s, and the density of air is 1.2 kg/m3.If the displacement amplitude of a 440-Hz sound wave is 10 µm, what is the intensity of the wave?

Accepted Answer

A) 0.16 W/m2 
B) 0.32 W/m2 
C) 12 W/m2 
D) 16 W/m2 
E) 32 W/m2 
A) 0.16 W/m2 
B) 0.32 W/m2 
C) 12 W/m2 
D) 16 W/m2 
E) 32 W/m2

Question 2

A standing wave in a pipe has nodes that are 1.2 m apart.What is the wavelength of the wave?

Accepted Answer

A) 0.6 m 
B) 1.2 m 
C) 1.8 m 
D) 2.4 m 
E) cannot tell without knowing which harmonic it is 
A) 0.6 m 
B) 1.2 m 
C) 1.8 m 
D) 2.4 m 
E) cannot tell without knowing which harmonic it is

Question 3

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 4

If the speed of sound is 340 m/s a plane flying at 400 m/s has a Mach number of:

Accepted Answer

A) 0.85 
B) 1.2 
C) 1.4 
D) 1.7 
E) 400 
A) 0.85 
B) 1.2 
C) 1.4 
D) 1.7 
E) 400

Question 5

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 6

The "A" on a trumpet and a clarinet have the same pitch, but the two are clearly distinguishable.Which property is most important in enabling one to distinguish between these two instruments?

Accepted Answer

A) intensity 
B) fundamental frequency 
C) displacement amplitude 
D) pressure amplitude 
E) harmonic content 
A) intensity 
B) fundamental frequency 
C) displacement amplitude 
D) pressure amplitude 
E) harmonic content

Question 7

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 8

A 1024 Hz tuning fork is used to obtain a series of resonance levels in a gas column of variable length, with one end closed and the other open.The length of the column changes by 20 cm from resonance to resonance.From this data, the speed of sound in this gas is:

Accepted Answer

A) 20 m/s 
B) 51 m/s 
C) 102 m/s 
D) 205 m/s 
E) 410 m/s 
A) 20 m/s 
B) 51 m/s 
C) 102 m/s 
D) 205 m/s 
E) 410 m/s

Question 9

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 10

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 11

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 12

The difference between transverse and longitudinal waves:

Accepted Answer

A) depends on the frequency of the wave 
B) depends on the wavelength of the wave 
C) depends on the direction of propagation of the wave 
D) depends on the direction of oscillation of the medium relative to the direction of propagation of the wave 
E) there is no difference, they are just two ways of describing the same phenomenon 
A) depends on the frequency of the wave 
B) depends on the wavelength of the wave 
C) depends on the direction of propagation of the wave 
D) depends on the direction of oscillation of the medium relative to the direction of propagation of the wave 
E) there is no difference, they are just two ways of describing the same phenomenon

Question 13

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

Question 14

What is a wavefront?

Accepted Answer

A) A set of points on a wave that are all traveling in the same direction. 
B) The front of the wave is the highest point on the wave. 
C) The front of the wave faces the direction the wave is traveling. 
D) A set of points on a wave that all have the same wavelength. 
E) A set of points on a wave that all have the same displacement. 
A) A set of points on a wave that are all traveling in the same direction. 
B) The front of the wave is the highest point on the wave. 
C) The front of the wave faces the direction the wave is traveling. 
D) A set of points on a wave that all have the same wavelength. 
E) A set of points on a wave that all have the same displacement.

Question 15

In each of the following two situations a source emits sound with a frequency of 1000 Hz.In situation I the source is moving at 100 m/s toward an observer at rest.In situation II the observer is moving at 100 m/s toward the source, which is stationary.The speed of sound is 340 m/s.The frequencies heard by the observers in the two situations are:

Accepted Answer

A) I: 1417 Hz; II: 1294 Hz 
B) I: 1417 Hz; II: 1417 Hz 
C) I: 1294 Hz; II: 1294 Hz 
D) I: 773 Hz; II: 706 Hz 
E) I: 773 Hz; II: 773 Hz 
A) I: 1417 Hz; II: 1294 Hz 
B) I: 1417 Hz; II: 1417 Hz 
C) I: 1294 Hz; II: 1294 Hz 
D) I: 773 Hz; II: 706 Hz 
E) I: 773 Hz; II: 773 Hz

Question 16

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 17

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 18

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 19

An organ pipe with one end open and the other closed is operating at one of its resonant frequencies.The open and closed ends are respectively:

Accepted Answer

A) pressure node, pressure node 
B) pressure node, displacement node 
C) displacement antinode, pressure node 
D) displacement node, displacement node 
E) pressure antinode, pressure antinode 
A) pressure node, pressure node 
B) pressure node, displacement node 
C) displacement antinode, pressure node 
D) displacement node, displacement node 
E) pressure antinode, pressure antinode

Question 20

Two small identical speakers are connected (in phase)to the same source.The speakers are 3 m apart and at ear level.An observer stands at X, 4 m in front of one speaker as shown.If the amplitudes are not changed, the sound he hears will be least intense if the wavelength is:

Accepted Answer

A) 1 m 
B) 2 m 
C) 3 m 
D) 4 m 
E) 5 m 
A) 1 m 
B) 2 m 
C) 3 m 
D) 4 m 
E) 5 m

Exam 17: Waves II

The speed of sound in air is 340 m/s, and the density of air is 1.2 kg/m3.If the displacement amplitude of a 440-Hz sound wave is 10 µm, what is the intensity of the wave?

A standing wave in a pipe has nodes that are 1.2 m apart.What is the wavelength of the wave?

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:

If the speed of sound is 340 m/s a plane flying at 400 m/s has a Mach number of:

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 "A" on a trumpet and a clarinet have the same pitch, but the two are clearly distinguishable.Which property is most important in enabling one to distinguish between these two instruments?

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 1024 Hz tuning fork is used to obtain a series of resonance levels in a gas column of variable length, with one end closed and the other open.The length of the column changes by 20 cm from resonance to resonance.From this data, the speed of sound in this gas is:

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:

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:

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

The difference between transverse and longitudinal waves:

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?

What is a wavefront?

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?

An organ pipe with one end open and the other closed is operating at one of its resonant frequencies.The open and closed ends are respectively:

Two small identical speakers are connected (in phase)to the same source.The speakers are 3 m apart and at ear level.An observer stands at X, 4 m in front of one speaker as shown.If the amplitudes are not changed, the sound he hears will be least intense if the wavelength is:

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The speed of sound in air is 340 m/s, and the density of air is 1.2 kg/m³.If the displacement amplitude of a 440-Hz sound wave is 10 µm, what is the intensity of the wave?

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:

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?