Question 1

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 2

The longitudinal displacement of a mass element in a medium as a sound wave passes through it is given by s = sm cos (kx - ωt). Consider a sound wave of frequency 440 Hz and wavelength 0.75m. If sm = 12 µm, what is the displacement of an element of air located at x = 1.2 m at time t = 0.11 s?

Accepted Answer

A)  3.7 µm 
B)  4.9 µm 
C)  6.0 µm 
D)  8.2 µm 
E)  12 µm 
A)  3.7 µm 
B)  4.9 µm 
C)  6.0 µm 
D)  8.2 µm 
E)  12 µm

Question 3

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 4

If I0 = 10-12 W/m2, and I = 4.5 x 10-8 W/m2, what is log (I/I0)?

Accepted Answer

A)  4.5 x 104 
B)  18 
C)  11 
D)  4.7 
E)  3.7 
A)  4.5 x 104 
B)  18 
C)  11 
D)  4.7 
E)  3.7

Question 5

At points in 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 6

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 7

A stationary source emits a sound wave of frequency f. If it were possible for a man to travel toward the source at the speed of sound, he would observe the emitted sound to have a frequency of:

Accepted Answer

A)  0 
B)  f/2 
C)  2f/3 
D)  2f 
E)  infinity 
A)  0 
B)  f/2 
C)  2f/3 
D)  2f 
E)  infinity

Question 8

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)  58 Hz 
B)  500 Hz 
C)  1000 Hz 
D)  2000 Hz 
E)  5800 Hz 
A)  58 Hz 
B)  500 Hz 
C)  1000 Hz 
D)  2000 Hz 
E)  5800 Hz

Question 9

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 10

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 11

Two identical tuning forks vibrate at 256 Hz. One of them is then loaded with a drop of wax, after which 6 beats per second are heard. The frequency of the loaded tuning fork is:

Accepted Answer

A)  250 Hz 
B)  253 Hz 
C)  256 Hz 
D)  259 Hz 
E)  262 Hz 
A)  250 Hz 
B)  253 Hz 
C)  256 Hz 
D)  259 Hz 
E)  262 Hz

Question 12

Two sound waves are traveling through the same medium. They have the same amplitude, wavelength, and direction of travel. If the phase difference between them is 7π, the type of interference they exhibit is:

Accepted Answer

A)  fully constructive 
B)  fully destructive 
C)  indeterminate 
D)  partially constructive 
E)  partially destructive 
A)  fully constructive 
B)  fully destructive 
C)  indeterminate 
D)  partially constructive 
E)  partially destructive

Question 13

The Doppler shift formula for the frequency detected is where f ' is the frequency emitted, v is the speed of sound, vD is the speed of the detector, and vs is the speed of the source. Suppose the source is traveling at 5 m/s away from the detector, the detector is traveling at 7 m/s toward the source, and there is a 3 m/s wind blowing from the source toward the detector. The values that should be substituted into the Doppler shift equation are:

Accepted Answer

A)  vD = 7 m/s and vs = 5 m/s 
B)  vD = 10 m/s and vs = 8 m/s 
C)  vD = 4 m/s and vs = 2 m/s 
D)  vD = 10 m/s and vs = 2 m/s 
E)  vD = 4 m/s and vs = 8 m/s 
A)  vD = 7 m/s and vs = 5 m/s 
B)  vD = 10 m/s and vs = 8 m/s 
C)  vD = 4 m/s and vs = 2 m/s 
D)  vD = 10 m/s and vs = 2 m/s 
E)  vD = 4 m/s and vs = 8 m/s

Question 14

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

Accepted Answer

A)  π/6 
B)  π/4 
C)  π/2 
D)  π 
E)  3π/2 
A)  π/6 
B)  π/4 
C)  π/2 
D)  π 
E)  3π/2

Question 15

The bulk modulus of water is 2.2 x 109 Pa, and its density is 1.0 x 103 kg/m3. What is the speed of sound in water?

Accepted Answer

A)  1.5 x 103 m/s 
B)  2.2 x 103 m/s 
C)  3.5 x 103 m/s 
D)  4.5 x 103 m/s 
E)  2.2 x 106 m/s 
A)  1.5 x 103 m/s 
B)  2.2 x 103 m/s 
C)  3.5 x 103 m/s 
D)  4.5 x 103 m/s 
E)  2.2 x 106 m/s

Question 16

The diagram shows four situations in which a source of sound S and a detector D are either moving or stationary. The arrows indicate the directions of motion. The speeds (when not zero) are all the same. (Note that the detector in situation 3 is stationary). Rank the situations according to the apparent frequency of the source, lowest to highest.

Accepted Answer

A)  1, 2, 3, 4 
B)  4, 3, 2, 1 
C)  1, 3, 4, 2 
D)  2, 1, 4, 3 
E)  None of the above 
A)  1, 2, 3, 4 
B)  4, 3, 2, 1 
C)  1, 3, 4, 2 
D)  2, 1, 4, 3 
E)  None of the above

Question 17

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 18

Two identical strings, A and B, have nearly the same tension. When they both vibrate in their fundamental resonant modes, there is a beat of 3 Hz. When string B is tightened slightly, to increase the tension, the beat frequency becomes 6 Hz. This means:

Accepted Answer

A)  that before tightening A had a higher frequency than B, but after tightening, B has a higher frequency than A 
B)  that before tightening B had a higher frequency than A, but after tightening, A has a higher frequency than B 
C)  that before and after tightening A has a higher frequency than B 
D)  that before and after tightening B has a higher frequency than A 
E)  none of the above 
A)  that before tightening A had a higher frequency than B, but after tightening, B has a higher frequency than A 
B)  that before tightening B had a higher frequency than A, but after tightening, A has a higher frequency than B 
C)  that before and after tightening A has a higher frequency than B 
D)  that before and after tightening B has a higher frequency than A 
E)  none of the above

Question 19

Take the speed of sound to be 340 m/s. A thunder clap is heard about 3 s after the lightning is seen. The source of both light and sound is:

Accepted Answer

A)  moving overhead faster than the speed of sound 
B)  emitting a much higher frequency than is heard 
C)  emitting a much lower frequency than is heard 
D)  about 1000 m away 
E)  much more than 1000 m away 
A)  moving overhead faster than the speed of sound 
B)  emitting a much higher frequency than is heard 
C)  emitting a much lower frequency than is heard 
D)  about 1000 m away 
E)  much more than 1000 m away

Question 20

A stationary source generates 5.0 Hz water waves whose speed is 2.0 m/s. A boat is approaching the source at 1.0 m/s. The frequency of these waves, as observed by a person in the boat, is:

Accepted Answer

A)  2.5 Hz 
B)  5.0 Hz 
C)  7.5 Hz 
D)  15 Hz 
E)  30 Hz 
A)  2.5 Hz 
B)  5.0 Hz 
C)  7.5 Hz 
D)  15 Hz 
E)  30 Hz

Exam 17: Waves II

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:

The longitudinal displacement of a mass element in a medium as a sound wave passes through it is given by s = sm cos (kx - ωt). Consider a sound wave of frequency 440 Hz and wavelength 0.75m. If sm = 12 µm, what is the displacement of an element of air located at x = 1.2 m at time t = 0.11 s?

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:

If I0 = 10-12 W/m2, and I = 4.5 x 10-8 W/m2, what is log (I/I0)?

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

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

A stationary source emits a sound wave of frequency f. If it were possible for a man to travel toward the source at the speed of sound, he would observe the emitted sound to have a frequency of:

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:

What is a wavefront?

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:

Two identical tuning forks vibrate at 256 Hz. One of them is then loaded with a drop of wax, after which 6 beats per second are heard. The frequency of the loaded tuning fork is:

Two sound waves are traveling through the same medium. They have the same amplitude, wavelength, and direction of travel. If the phase difference between them is 7π, the type of interference they exhibit is:

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

The bulk modulus of water is 2.2 x 109 Pa, and its density is 1.0 x 103 kg/m3. What is the speed of sound in water?

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?

Two identical strings, A and B, have nearly the same tension. When they both vibrate in their fundamental resonant modes, there is a beat of 3 Hz. When string B is tightened slightly, to increase the tension, the beat frequency becomes 6 Hz. This means:

Take the speed of sound to be 340 m/s. A thunder clap is heard about 3 s after the lightning is seen. The source of both light and sound is:

A stationary source generates 5.0 Hz water waves whose speed is 2.0 m/s. A boat is approaching the source at 1.0 m/s. The frequency of these waves, as observed by a person in the boat, is:

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The longitudinal displacement of a mass element in a medium as a sound wave passes through it is given by s = s_m cos (kx - ωt). Consider a sound wave of frequency 440 Hz and wavelength 0.75m. If s_m = 12 µm, what is the displacement of an element of air located at x = 1.2 m at time t = 0.11 s?

If I₀ = 10^-12 W/m², and I = 4.5 x 10^-8 W/m², what is log (I/I₀)?

The bulk modulus of water is 2.2 x 10⁹ Pa, and its density is 1.0 x 10³ kg/m³. What is the speed of sound in water?