Question 1

If the length of a piano wire (of given density) is increased by 5%, what approximate change in tension is necessary to keep its fundamental frequency unchanged?

Accepted Answer

A)  decrease of 10% 
B)  decrease of 5% 
C)  increase of 5% 
D)  increase of 10% 
E)  increase of 20% 
A)  decrease of 10% 
B)  decrease of 5% 
C)  increase of 5% 
D)  increase of 10% 
E)  increase of 20%

Question 2

If the speed of sound is 340 m/s, the two lowest frequencies of an 0.5 m organ pipe, closed at one end, are approximately:

Accepted Answer

A)  170 and 340 Hz 
B)  170 and 510 Hz 
C)  340 and 680 Hz 
D)  340 and 1020 Hz 
E)  57 and 170 Hz 
A)  170 and 340 Hz 
B)  170 and 510 Hz 
C)  340 and 680 Hz 
D)  340 and 1020 Hz 
E)  57 and 170 Hz

Question 3

A vibrating tuning fork is held over a water column with one end closed and the other open. As the water level is allowed to fall, a loud sound is heard for water levels separated by 17 cm. If the speed of sound in air is 340 m/s, the frequency of the tuning fork is:

Accepted Answer

A)  500 Hz 
B)  1000 Hz 
C)  2000 Hz 
D)  5780 Hz 
E)  578,000 Hz 
A)  500 Hz 
B)  1000 Hz 
C)  2000 Hz 
D)  5780 Hz 
E)  578,000 Hz

Question 4

Two stationary tuning forks (350 and 352 Hz) are struck simultaneously. The resulting sound is observed to:

Accepted Answer

A)  beat with a frequency of 2 beats/s 
B)  beat with a frequency of 351 beats/s 
C)  be loud but not beat 
D)  be Doppler shifted by 2 Hz 
E)  have a frequency of 702 Hz 
A)  beat with a frequency of 2 beats/s 
B)  beat with a frequency of 351 beats/s 
C)  be loud but not beat 
D)  be Doppler shifted by 2 Hz 
E)  have a frequency of 702 Hz

Question 5

The intensity of sound wave A is 100 times that of sound wave B. Relative to wave B the sound level of wave A is:

Accepted Answer

A)  -2 db 
B)  +2 db 
C)  +10 db 
D)  +20 db 
E)  +100 db 
A)  -2 db 
B)  +2 db 
C)  +10 db 
D)  +20 db 
E)  +100 db

Question 6

A column of argon is open at one end and closed at the other. The shortest length of such a column that will resonate with a 200 Hz tuning fork is 42.5 cm. The speed of sound in argon must be:

Accepted Answer

A)  85.0 m/s 
B)  170 m/s 
C)  340 m/s 
D)  470 m/s 
E)  940 m/s 
A)  85.0 m/s 
B)  170 m/s 
C)  340 m/s 
D)  470 m/s 
E)  940 m/s

Question 7

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

Question 8

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 9

Two notes are an "octave" apart. The ratio of their frequencies is:

Accepted Answer

A)  8 
B)  10 
C)    
D)  2 
E)    
A)  8 
B)  10 
C)    
D)  2 
E)

Question 10

To raise the pitch of a certain piano string, the piano tuner:

Accepted Answer

A)  loosens the string 
B)  tightens the string 
C)  shortens the string from the string 
D)  lengthens the string 
E)  removes some mass 
A)  loosens the string 
B)  tightens the string 
C)  shortens the string from the string 
D)  lengthens the string 
E)  removes some mass

Question 11

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 12

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 13

During a time interval of exactly one period of vibration of a tuning fork, the emitted sound travels a distance:

Accepted Answer

A)  equal to the length of the tuning fork 
B)  equal to twice the length of the tuning fork 
C)  of about 330 m 
D)  which decreases with time 
E)  of one wavelength in air 
A)  equal to the length of the tuning fork 
B)  equal to twice the length of the tuning fork 
C)  of about 330 m 
D)  which decreases with time 
E)  of one wavelength in air

Question 14

A piano wire has length L and mass M. If its fundamental frequency is f, its tension is:

Accepted Answer

A)  2Lf/m 
B)  4MLf 
C)  2Mf2/L 
D)  4f2L3/M 
E)  4LMf2 
A)  2Lf/m 
B)  4MLf 
C)  2Mf2/L 
D)  4f2L3/M 
E)  4LMf2

Question 15

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. The sound she hears will be most intense if the wavelength is:

Accepted Answer

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

Question 16

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 17

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 18

At points is a sound wave where the gas is maximally compressed, the pressure

Accepted Answer

A)  is a maximum 
B)  is a minimum 
C)  is equal to the ambient value 
D)  is greater than the ambient value but less than the maximum 
E)  is less than the ambient value but greater than the minimum 
A)  is a maximum 
B)  is a minimum 
C)  is equal to the ambient value 
D)  is greater than the ambient value but less than the maximum 
E)  is less than the ambient value but greater than the minimum

Question 19

A fire whistle emits a tone of 170 Hz. Take the speed of sound in air to be 340 m/s. The wavelength of this sound is about:

Accepted Answer

A)  0.5 m 
B)  1.0 m 
C)  2.0 m 
D)  3.0 m 
E)  340 m 
A)  0.5 m 
B)  1.0 m 
C)  2.0 m 
D)  3.0 m 
E)  340 m

Question 20

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

Accepted Answer

A)  60 
B)  6.6 
C)  6.06 
D)  600 
E)  12 
A)  60 
B)  6.6 
C)  6.06 
D)  600 
E)  12

Exam 17: Waves II

If the length of a piano wire (of given density) is increased by 5%, what approximate change in tension is necessary to keep its fundamental frequency unchanged?

If the speed of sound is 340 m/s, the two lowest frequencies of an 0.5 m organ pipe, closed at one end, are approximately:

A vibrating tuning fork is held over a water column with one end closed and the other open. As the water level is allowed to fall, a loud sound is heard for water levels separated by 17 cm. If the speed of sound in air is 340 m/s, the frequency of the tuning fork is:

Two stationary tuning forks (350 and 352 Hz) are struck simultaneously. The resulting sound is observed to:

The intensity of sound wave A is 100 times that of sound wave B. Relative to wave B the sound level of wave A is:

A column of argon is open at one end and closed at the other. The shortest length of such a column that will resonate with a 200 Hz tuning fork is 42.5 cm. The speed of sound in argon must be:

To produce beats it is necessary to use two waves:

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 notes are an "octave" apart. The ratio of their frequencies is:

To raise the pitch of a certain piano string, the piano tuner:

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?

During a time interval of exactly one period of vibration of a tuning fork, the emitted sound travels a distance:

A piano wire has length L and mass M. If its fundamental frequency is f, its tension is:

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. The sound she hears will be most intense if the wavelength is:

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

At points is a sound wave where the gas is maximally compressed, the pressure

A fire whistle emits a tone of 170 Hz. Take the speed of sound in air to be 340 m/s. The wavelength of this sound is about:

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

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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 (in $\mu$ W/cm²) is: