Deck 14: Waves and Sound

Question 1

What is the frequency of the wave shown in the figure?

A)0.5 Hz.
B)1 Hz.
C)2 Hz.
D)4 Hz.
E)It cannot be determined from the given information.

Answer 1

0.5 Hz.

Question 2

What is the wavelength of the wave shown in the figure?

A)8 m.
B)4 m.
C)2 m.
D)1 m.
E)It cannot be determined from the given information.

Answer 2

It cannot be determined from the given information.

Question 3

When a certain string is under tension T,the speed of a wave in the string is v.What will be the speed of a wave in the string if the tension is increased to 2T without changing the mass or length of the string?

A)v/2
B)v/
C)v
D)2v
E)4v

Answer 3

v

Question 4

Four waves are described by the following equations,where distances are measured in meters and times in seconds.
I.y = 0.12 cos(3x - 21t)
II.y = 0.15 sin(6x + 42t)
III.y = 0.13 cos(6x + 21t)
IV.y = -0.23 sin(3x - 42t)
Which of these waves have the same speed?

A)I and II
B)I and III
C)II and III
D)III and IV
E)II and IV

Question 5

Why does the intensity of waves from a small source decrease with the square of the distance from the source?

A)The waves run out of energy as they travel.
B)The waves spread out as they travel.
C)The medium through which the waves travel absorbs the energy of the waves.
D)The waves slow down as they travel away from the source.
E)The frequency of the waves decreases as they get farther from the source.

Question 6

As you are moving very quickly toward a speaker emitting a pure tone,which characteristics of the sound get larger? (There may be more than one correct choice. )

A)frequency
B)amplitude
C)wavelength
D)period
E)loudness

Question 7

What characteristics of a sound wave are related to the "pitch" of a musical note? (There could be more than one correct choice. )

A)amplitude
B)wavelength
C)frequency
D)period

Question 8

In many cartoon shows,a character runs off a cliff,realizes his predicament,and lets out a scream.He continues to scream as he falls.If the physical situation is portrayed correctly,from the vantage point of an observer at the foot of the cliff,the pitch of the scream as he falls should be

A)higher than the original pitch and constant.
B)higher than the original pitch and increasing as he falls.
C)lower than the original pitch and constant.
D)lower than the original pitch and decreasing as he falls.
E)It is impossible to predict.

Question 9

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.

Question 10

A string of mass m is under tension,and the speed of a wave in the string is v.What will be the speed of a wave in the string if the mass of the string is increased to 2m but with no change in the length or tension?

A)v/2
B)v/
C)v
D)2v
E)4v

Question 11

When a guitar is tuned to adjust it pitch,what is it that is changed?

A)The wavelength of the fundamental.
B)The frequency of the fundamental.
C)The amplitude of the fundamental.

Question 12

Which one of the curves shown in the figure best represents the variation of wave speed v as a function of tension for transverse waves on a stretched string?

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

Question 13

Sound A has a high pitch and sound B has a low pitch.Which of the following statements about these two sounds are correct? (There could be more than one correct choice. )

A)The wavelength of A is longer than the wavelength of B.
B)The period of A is shorter than the period of B.
C)The frequency of A is greater than the frequency of B.
D)Sound B travels faster than sound B through air.
E)The amplitude of A is larger than the amplitude of B.

Question 14

Suppose that a sound source is emitting waves uniformly in all directions.If you move to a point twice as far away from the source,the frequency of the sound will be

A)unchanged.
B)half as great.
C)one-fourth as great.
D)twice as great.

Question 15

The intensity of the waves from a point source at a distance d from the source is I.At what distance from the sources is the intensity equal to 2I?

A)d/2
B)d/
C)d/4
D)d/8

Question 16

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

Question 17

The intensity of the waves from a point source at a distance d from the source is I.What is the intensity at a distance 2d from the source?

A)4I
B)2I
C)I/2
D)I/4
E)I/

Question 18

A string of length L is under tension,and the speed of a wave in the string is v.What will be the speed of a wave in the string if the length is increased to 2L but with no change in the mass or tension?

A)v/2
B)v/
C)v
D)2v
E)4v

Question 19

In many cartoon shows,a character runs off a cliff,realizes his predicament,and lets out a scream.He continues to scream as he falls.If the physical situation is portrayed correctly,from the vantage point of an observer at the top of the cliff leaning over the edge,the pitch of the scream as he falls should be

A)higher than the original pitch and constant.
B)higher than the original pitch and increasing as he falls.
C)lower than the original pitch and constant.
D)lower than the original pitch and decreasing as he falls.
E)It is impossible to predict.

Question 20

Four waves are described by the following equations,where distances are measured in meters and times in seconds.
I.y = 0.12 cos(3x - 21t)
II.y = 0.15 sin(6x + 42t)
III.y = 0.13 cos(6x + 21t)
IV.y = -0.23 sin(3x - 42t)
Which of these waves have the same period?

A)I and III,and also II and IV
B)I and IV,and also II and III
C)I and II,and also III and IV
D)All of them have the same period.
E)They all have different periods.

Question 21

A pipe of length L that is closed at one end and open at the other end is resonating at its fundamental frequency.Which statement about the sound is correct?

A)The wavelength is 4L and there is a displacement node at the pipe's open end.
B)The wavelength is 4L and there is a displacement antinode at the pipe's open end.
C)The wavelength is L and there is a displacement node at the pipe's open end.
D)The wavelength is L and there is a displacement antinode at the pipe's open end.

Question 22

Consider the standing wave on a guitar string and the sound wave generated by the string as a result of this vibration.What do these two waves have in common? (There may be more than one correct choice. )

A)They have the same wavelength.
B)They have the same speed.
C)They have the same frequency.
D)They have the same amplitude.
E)They have the same period.

Question 23

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

Question 24

Two pure tones are sounded together and a particular beat frequency is heard.What happens to the beat frequency if the frequency of one of the tones is increased?

A)It increases.
B)It decreases.
C)It does not change.
D)It could either increase or decrease.

Question 25

A string fixed at both ends is vibrating in one of its harmonics.If we now increase only the frequency at which the string is vibrating,which of the following characteristics do we also increase? (There could be more than one correct choice. )

A)the speed of the traveling waves on the string
B)the period of the traveling waves on the string
C)the wavelength of the traveling waves on the string
D)the amplitude of the traveling waves on the string
E)none of the above

Question 26

In a resonating pipe that is open at both ends,there

A)are displacement nodes at each end.
B)are displacement antinodes at each end.
C)is a displacement node at one end and a displacement antinode at the other end.
D)None of the above choices are correct.

Question 27

A person stands between two speakers driven by the same source.Each speaker produces a tone with a frequency of 200 Hz on a day when the speed of sound is 330 m/s.The person is 1.65 m from one speaker and 4.95 m from the other.What type of interference does the person perceive?

A)constructive
B)destructive
C)both constructive and destructive
D)neither constructive nor destructive

Question 28

If a guitar string has a fundamental frequency of 500 Hz,which one of the following frequencies can set the string into resonant vibration?

A)250 Hz
B)750 Hz
C)1500 Hz
D)1750 Hz

Question 29

The lowest tone to resonate in a pipe of length L that is closed at one end but open at the other end is 200 Hz.Which one of the following frequencies will not resonate in that pipe?

A)200 Hz
B)400 Hz
C)600 Hz
D)1000 Hz
E)1400 Hz

Question 30

An pipe of length L that is open at both ends is resonating at its fundamental frequency.Which statement about the sound is correct?

A)The wavelength is 2L and there is a displacement node at the pipe's midpoint.
B)The wavelength is 2L and there is a displacement antinode at the pipe's midpoint.
C)The wavelength is L and there is a displacement node at the pipe's midpoint.
D)The wavelength is L and there is a displacement antinode at the pipe's midpoint.

Question 31

In a resonating pipe that is open at one end and closed at the other,there

A)are displacement nodes at each end.
B)are displacement antinodes at each end.
C)is a displacement node at the open end and a displacement antinode at the closed end.
D)is a displacement node at the closed end and a displacement antinode at the open end.

Question 32

A music tuner uses a 554-Hz C# tuning fork to tune the frequency of a musical instrument.If the tuner hears a beat frequency of 2 Hz,what is the frequency of the instrument?

A)It must be 556 Hz.
B)It must be 552 Hz.
C)It could be either 556 Hz or 552 Hz.
D)It could be either 553 Hz or 555 Hz.
E)It is neither 556 Hz or 552 Hz.

Question 33

In a resonating pipe that is open at one end and closed at the other end,there

A)are displacement nodes at each end.
B)are displacement antinodes at each end.
C)is a displacement node at the open end and a displacement antinode at the closed end.
D)is a displacement node at the closed end and a displacement antinode at the open end.

Question 34

The lowest tone to resonate in pipe of length L that is open at both ends is 200 Hz.Which one of the following frequencies will not resonate in the same pipe?

A)200 Hz
B)400 Hz
C)600 Hz
D)800 Hz
E)900 Hz

Question 35

Consider a pipe of length L that is open at one end and closed at the other end.What are the wavelengths of the three lowest-pitch tones produced by this pipe?

A)4L,2L,L
B)2L,L,L/2
C)2L,L,2 L/3
D)4L,4L/3,4L/5

Question 36

If a string fixed at both ends resonates in its fundamental mode with a frequency of 150 Hz,at which of the following frequencies will it not resonate? (There could be more than one correct choice. )

A)75 Hz
B)300 Hz
C)450 Hz
D)500 Hz
E)600 Hz

Question 37

Consider a pipe of length L that is open at both ends.What are the wavelengths of the three lowest-pitch tones produced by this pipe?

A)4L,2L,L
B)2L,L,L/2
C)2L,L,2L/3
D)4L,4L/3,4L/5

Question 38

A stretched string is observed to have four equal segments in a standing wave driven at a frequency of 480 Hz.What driving frequency will set up a standing wave with five equal segments?

A)600 Hz
B)360 Hz
C)240 Hz
D)120 Hz

Question 39

An organ pipe of length L that is open at one end resonates in its third harmonic with a wavelength of 2L/3.Is the other end of the pipe closed or open?

A)closed
B)open
C)We cannot tell from the information provided.

Question 40

Two strings both vibrate at exactly 819 Hz.The tension in one of them is then increased slightly.As a result,six beats per second are heard when both strings vibrate.What is the new frequency of the string that was tightened?

A)825 Hz
B)813 Hz
C)822 Hz
D)816 Hz

Question 41

A wire that is 1.0 m long with a mass of 90 g is under a tension of 710 N.When a transverse wave travels on the wire,its wavelength is 0.10 m and its amplitude is 6.5 mm.What is the frequency of this wave?

A)890 Hz
B)920 Hz
C)1000 Hz
D)1200 Hz
E)1500 Hz

Question 42

A crane lifts a 2500-kg beam at a steady rate of 15 cm/s using a steel cable whose mass per unit length is 0.65 kg/m.What is the speed of transverse waves on this cable?

A)230 m/s
B)580 m/s
C)1200 m/s
D)1900 m/s
E)190 m/s

Question 43

A tsunami,an ocean wave generated by an earthquake,propagates along the open ocean at 700 km/hr and has a wavelength of 750 km.What is the frequency of the waves in such a tsunami?

A)0.93 Hz
B)0.00026 Hz
C)1.1 Hz
D)6.8 Hz
E)0.15 Hz

Question 44

A 10-gram wire that is 6.0 m long is under tension.When a transverse wave of frequency 280 Hz travels along the wire,its wavelength is 0.60 m,and its amplitude is 8.4 mm.How much time does it take for a crest of the transverse wave to travel the length of the wire?

A)36 ms
B)31 ms
C)40 ms
D)44 ms
E)49 ms

Question 45

A fisherman fishing from a pier observes that the float on his line bobs up and down,taking 2.4 s to move from its highest point to its lowest point.He also estimates that the distance between adjacent wave crests is 48 m.What is the speed of the waves going past the pier?

A)1.0 m/s
B)20 m/s
C)10 m/s
D)5.0 m/s
E)120 m/s

Question 46

An earthquake generates three kinds of waves: surface waves (L-waves),which are the slowest and weakest,shear (S)waves,which are transverse waves and carry most of the energy,and pressure (P)waves,which are longitudinal waves and are the fastest.The speed of P waves is approximately 7 km/s,and that of S waves is about 4 km/s.People do not generally feel the P waves,but animals seem to be sensitive to them.If a person reports that her dog started barking 20 seconds "before the earthquake," then approximately how far was the origin of the earthquake?

A)100 km
B)200 km
C)300 km
D)400 km
E)500 km

Question 47

A 1.1-kg uniform bar of metal is 0.40 m long and has a diameter of 2.0 cm.When someone bangs one end of this bar,a 1.5 MHz shock wave is travels along the length of the bar and reaches the other end in 0.12 ms.What is the wavelength of the shock wave in the metal?

A)2.2 mm
B)2.6 mm
C)3.0 mm
D)3.4 mm
E)3.8 mm

Question 48

Transverse waves travel at
In a string that is subjected to a tension of
If the string is
Long,what is its mass?

A)0.515 kg
B)0.216 kg
C)0.366 kg
D)0.597 kg

Question 49

A piano wire of linear mass density 0.0050 kg/m is under a tension of 1350 N.What is the wave speed in this wire?

A)130 m/s
B)260 m/s
C)520 m/s
D)1040 m/s

Question 50

What is the wave speed in a brass wire with a radius of 0.500 mm stretched with a tension of 125 N? The density of brass is 8.60 × 10³ kg/m³.

A)0.121 m/s
B)100 m/s
C)136 m/s
D)500 m/s
E)68.8 m/s

Question 51

The density of aluminum is 2700 kg/m³.If transverse waves travel at
In an aluminum wire of diameter
What is the tension on the wire?

A)65 N
B)39 N
C)52 N
D)78 N

Question 52

The speed of sound in steel is 5000 m/s.What is the wavelength of a sound wave of frequency
In steel?

A)7.58 m
B)2.41 m
C)1.21 m
D)0.829 m
E)0.132 m

Question 53

Two steel wires are stretched with the same tension.The first wire has a diameter of 0.610 mm and the second wire has a diameter of 0.910 mm.If the speed of waves traveling along the first wire is 54.0 m/s,what is the speed of waves traveling along the second wire?

A)24.9 m/s
B)27.2 m/s
C)36.2 m/s
D)81.0 m/s
E)100 m/s

Question 54

A crane lifts a 2500-kg beam using a steel cable whose mass per unit length is 0.650 kg/m.What is the speed of transverse waves on this cable if the upward acceleration of the beam is a steady 3.00 m/s²?

A)194 m/s
B)578 m/s
C)1220 m/s
D)1880 m/s
E)222 m/s

Question 55

Crests of an ocean wave pass a pier every
If the waves are moving at
What is the wavelength of the ocean waves?

A)56 m
B)28 m
C)64 m
D)48 m

Question 56

What is the frequency of a pressure wave of wavelength 2.5 m that is traveling at 1400 m/s?

A)178 Hz
B)1.78 kHz
C)560 Hz
D)5.6 kHz

Question 57

A 2.31-kg rope is stretched between supports that are 10.4 m apart,and has a tension in it of 49.2 N.If one end of the rope is slightly tweaked,how long will it take for the resulting disturbance to reach the other end?

A)0.699 s
B)0.720 s
C)0.664 s
D)0.615 s

Question 58

A 90-gram wire that is 1.0 m long is under tension.When a transverse wave of frequency 890 Hz travels down the wire,its wavelength is 0.10 m and its amplitude is 6.5 mm.What is the tension in the wire?

A)710 N
B)820 N
C)930 N
D)1,000 N
E)1,100 N

Question 59

If a wave has a speed of 362 m/s and a period of 4.17 ms,what is its wavelength?

A)1510 m
B)1.51 m
C)86.8 m
D)86,800 m
E)0.0115 m

Question 60

A 15-m rope is pulled taut with a tension of 140 N.It takes 0.545 s for a wave to propagate along the rope.What is the mass of the rope?

A)1.7 kg
B)2.1 kg
C)2.8 kg
D)5.1 kg
E)3.2 kg

Question 61

The speed of sound through the ground is about 6.0 km/s while the speed of sound in air is 343 m/s.A very powerful explosion occurs some distance away and you feel the ground vibrate 60 seconds before you hear the sound of the explosion.How far away is the explosion?

A)20 km
B)22 km
C)25 km
D)27 km
E)30 km

Question 62

At a distance of 15.0 m from a sound source,the intensity level is 60.0 dB.What is the intensity level (in decibels)at a point 2.00 m from the source if the source radiates equally in all directions?

A)55.7 dB
B)57.5 dB
C)75.5 dB
D)77.5 dB

Question 63

What are the wavelength (in meters)and frequency (in hertz)of a wave whose displacement is given by the equation y = 0.5 sin(0.20x + 120t),where x and y are in meters and t is in seconds?

A)10 m,0.50 Hz
B)5.0 m,10 Hz
C)19 m,120 Hz
D)31 m,19 Hz
E)0.20 m,120 Hz

Question 64

The intensity at a distance of 6.0 m from a source that is radiating equally in all directions is 6.0 × 10^-10 W/m².What is the intensity level in dB? The threshold of human hearing is 1.0 × 10^-12 W/m².

A)18 dB
B)23 dB
C)28 dB
D)32 dB

Question 65

A barking dog delivers about 1.0 mW of power,which is assumed to be uniformly distributed in all directions.What is the intensity level in decibels at a distance 5.00 m from the dog? The threshold of human hearing is 1.0 × 10^-12 W/m².

A)61 dB
B)63 dB
C)65 dB
D)68 dB

Question 66

If the intensity level by 15 identical engines in a garage is 100 dB,what is the intensity level generated by each one of these engines?

A)67 dB
B)13 dB
C)44 dB
D)88 dB

Question 67

Light from a laser forms a 1.31-mm diameter spot on a wall.If the light intensity in the spot is
What is the power output of the laser? Assume that all the light emitted by the laser hits the spot.

A)21.3 mW
B)13.2 mW
C)17.9 mW
D)24.7 mW

Question 68

What is the intensity of a 70-dB sound? The threshold of human hearing is 1.0 × 10^-12 W/m².

A)10^-4 W/m²
B)10^-5 W/m²
C)10^-6 W/m²
D)10^-7 W/m²

Question 69

By how many decibels does the intensity level of a sound decrease when you triple your distance from a source of sound?

A)9.5 dB
B)4.8 dB
C)6.0 dB
D)12 dB
E)3.0 dB

Question 70

Calculate the light intensity 1.45 m from a light bulb that radiates 100 W equally in all directions.

A)3.78 W/m²
B)4.36 W/m²
C)47.6 W/m²
D)54.7 W/m²

Question 71

The average intensity of sunlight impinging on Earth is measured to be about 1.4 kW/m².What is the power of sunlight emitted by the sun? (Earth-Sun distance = 1.5 × 10⁸ km,Earth radius = 6.4 × 10³ km)

A)4.0 × 10²⁶ W
B)3.2 × 10²² W
C)7.2 × 10¹⁴ W
D)7.6 × 10⁸ W

Question 72

What is the ratio of the intensities of two sounds with intensity levels of 70 dB and 40 dB?

A)10:1
B)100:1
C)1000:1
D)10,000:1

Question 73

Find the speed of an ocean wave whose displacement is given by the equation
Where x and y are in meters and t is in seconds.

A)2.5 m/s
B)1.9 m/s
C)3.5 m/s
D)4.5 m/s

Question 74

You double your distance from a sound source that is radiating equally in all directions.What happens to the intensity level of the sound? It drops by

A)2 dB.
B)3 dB.
C)6 dB.
D)8 dB.

Question 75

The intensity level is 65 dB at a distance 5.00 m from a barking dog.What would be a reasonable estimate for the intensity level if two identical dogs very close to each other were barking? You can ignore any interference effects.

A)65 dB
B)68 dB
C)130 dB
D)136 dB

Question 76

The sound intensity level 5.0 m from a point source is 95 dB.At what distance will it be 75 dB?

A)25 m
B)50 m
C)75 m
D)225 m

Question 77

Two motors in a factory are running at slightly different rates.One runs at 825.0 rpm and the other at
You hear the sound intensity increase and then decrease periodically due to wave interference.How long does it take between successive instances of the sound intensity increasing?

A)1.54 s
B)1.43 s
C)1.66 s
D)1.79 s

Question 78

The intensity at a distance of 6.0 m from a source that is radiating equally in all directions is 6.0 × 10^-10 W/m².What is the power emitted by the source?

A)2.1 × 10^-8 W
B)2.7 × 10^-7 W
C)2.1 × 10^-6 W
D)2.7 × 10^-5 W

Question 79

What is the intensity level in decibels of a sound with intensity 10^-3 W/m²? The threshold of human hearing is 1.0 × 10^-12 W/m².

A)30 dB
B)60 dB
C)90 dB
D)96 dB

Question 80

You drop a stone down a well that is 9.5 m deep.How long is it before you hear the splash? The speed of sound in air is 343 m/s and air resistance is negligible.

A)1.2 s
B)1.3 s
C)1.4 s
D)1.5 s
E)1.6 s