Question 1

The human ear can be sensitive to sound frequencies up to 20 kHz.What wavelength does this correspond to at normal temperature and pressure?

Accepted Answer

A) 0.165 m 
B) 165 cm 
C) 16.5 mm 
D) 1650 $\times$ 10-4 m 
E) 1.65 mm 
A) 0.165 m 
B) 165 cm 
C) 16.5 mm 
D) 1650 $\times$ 10-4 m 
E) 1.65 mm

Question 2

The intensity of a wave at a certain point is I.A second wave has twice the energy density and three times the speed of the first.What is the intensity of the second wave?

Accepted Answer

A) I 
B) 2I 
C) 3I 
D) 6I 
E) 2I/3 
A) I 
B) 2I 
C) 3I 
D) 6I 
E) 2I/3

Question 3

An oscillator tuned to a frequency of 1 kHz is dropped from a tall building.How does the frequency picked up by a stationary observer at the top of the building change with time?

Accepted Answer

A) The frequency will be lower than 1 kHz but does not change with time. 
B) The frequency will be lower than 1 kHz and decreases further with time. 
C) The frequency will be higher than 1 kHz but does not change with time. 
D) The frequency will be higher than 1 kHz and decreases further with time. 
E) The frequency stays at 1 kHz. 
A) The frequency will be lower than 1 kHz but does not change with time. 
B) The frequency will be lower than 1 kHz and decreases further with time. 
C) The frequency will be higher than 1 kHz but does not change with time. 
D) The frequency will be higher than 1 kHz and decreases further with time. 
E) The frequency stays at 1 kHz.

Question 4

The frequency of a car horn is f.What frequency is observed if both the car and the observer are at rest,but a wind is blowing toward the observer?

Accepted Answer

A) f 
B) greater than f 
C) less than f 
D) either greater or less than f 
E) far greater than f,depending on how wind speed compares with the speed of sound 
A) f 
B) greater than f 
C) less than f 
D) either greater or less than f 
E) far greater than f,depending on how wind speed compares with the speed of sound

Question 5

A stationary ship generates a sound signal at the bow and has a receiver system at the stern of the ship 100 m away.The signal arriving at the stern traveling directly through the air and the signal reflected from the sea bottom arrive at the sensor at the same time.If the velocity of sound in air is 331 m/s and in water is 1435 m/s,calculate the depth of water below the ship.

Accepted Answer

A) 434 m 
B) 422 m 
C) 217 m 
D) 211 m 
E) 192 m 
A) 434 m 
B) 422 m 
C) 217 m 
D) 211 m 
E) 192 m

Question 6

Workmen are digging up the road using pneumatic tools.If a single tool creates a noise level of 88 decibels a few meters away,calculate the noise level if four such tools were in operation the same distance away.

Accepted Answer

A) 176 dB 
B) 90 dB 
C) 352 dB 
D) 94 dB 
E) 92 dB 
A) 176 dB 
B) 90 dB 
C) 352 dB 
D) 94 dB 
E) 92 dB

Question 7

A sinusoidal wave train is moving along a string.The equation giving the displacement y of a point at coordinate x has the form   where the units are SI.The wavelength is

Accepted Answer

A) 8.0 cm 
B) 15 cm 
C) 6.0 m 
D) 12 m 
E) 60 m 
A) 8.0 cm 
B) 15 cm 
C) 6.0 m 
D) 12 m 
E) 60 m

Question 8

The sound level of a dog's bark is 50 dB.The intensity of a rock concert is 10,000 times that of the dog's bark.What is the sound level of the rock concert?

Accepted Answer

A) 10,050 dB 
B) 500,000 dB 
C) 90 dB 
D) 2000 dB 
E) 54 dB 
A) 10,050 dB 
B) 500,000 dB 
C) 90 dB 
D) 2000 dB 
E) 54 dB

Question 9

A train traveling at 90 km/h is blowing its whistle at 440 Hz as it crosses a level crossing.You are waiting at the crossing and hear the pitch of the whistle change as the train passes you.The sound you hear changes from a frequency of _____ to a frequency of _____.(Take the speed of sound to be 340 m/s.)

Accepted Answer

A) 475 Hz; 410 Hz 
B) 410 Hz; 475 Hz 
C) 408 Hz; 472 Hz 
D) 472 Hz; 408 Hz 
E) 598 Hz; 348 Hz 
A) 475 Hz; 410 Hz 
B) 410 Hz; 475 Hz 
C) 408 Hz; 472 Hz 
D) 472 Hz; 408 Hz 
E) 598 Hz; 348 Hz

Question 10

A jet engine emits a whine of frequency 3000 Hz.When the engine is moving directly away from an observer at half the speed of sound,an observer hears a frequency of

Accepted Answer

A) 1000 Hz 
B) 1500 Hz 
C) 2000 Hz 
D) 4500 Hz 
E) 6000 Hz 
A) 1000 Hz 
B) 1500 Hz 
C) 2000 Hz 
D) 4500 Hz 
E) 6000 Hz

Question 11

The power transmitted by any harmonic wave varies directly as

Accepted Answer

A) the period. 
B) the square root of the frequency. 
C) the amplitude. 
D) the amplitude squared. 
E) None of these is correct. 
A) the period. 
B) the square root of the frequency. 
C) the amplitude. 
D) the amplitude squared. 
E) None of these is correct.

Question 12

Which of the following statements about longitudinal and transverse pressure waves is NOT true?

Accepted Answer

A) Longitudinal pressure waves can travel through fluids. 
B) Transverse pressure waves can travel through fluids. 
C) Longitudinal pressure waves can travel through solids. 
D) Transverse pressure waves can travel through solids. 
E) Both longitudinal and transverse pressure waves transport energy. 
A) Longitudinal pressure waves can travel through fluids. 
B) Transverse pressure waves can travel through fluids. 
C) Longitudinal pressure waves can travel through solids. 
D) Transverse pressure waves can travel through solids. 
E) Both longitudinal and transverse pressure waves transport energy.

Question 13

A stationary ship generates a sound signal at the bow and has a receiver system at the stern of the ship 100 m away.The difference in time between the signal arriving at the stern traveling directly through the air and the signal reflected from the sea bottom is 0.5 second.If the velocity of sound in air is 331 m/s and in water is 1435 m/s,calculate the depth of water below the ship.

Accepted Answer

A) 1150 m 
B) 574 m 
C) 359 m 
D) 396 m 
E) 450 m 
A) 1150 m 
B) 574 m 
C) 359 m 
D) 396 m 
E) 450 m

Question 14

If you were to double the amplitude and halve the frequency of a wave on a string while keeping the amplitude of the wave constant,the rate at which energy is delivered by the wave would

Accepted Answer

A) double. 
B) quadruple. 
C) be reduced 50%. 
D) be reduced to 25% of its previous value. 
E) be unchanged. 
A) double. 
B) quadruple. 
C) be reduced 50%. 
D) be reduced to 25% of its previous value. 
E) be unchanged.

Question 15

The picture on the right represents the wavefronts of a supersonic flight.The angle $\theta$ = 40S1U1P1$\circ$S1S1P0.If the speed of sound is 300 m/s,what is the speed of the plane?

Accepted Answer

A) 360 m/s 
B) 330 m/s 
C) 300 m/s 
D) 390 m/s 
E) 470 m/s 
A) 360 m/s 
B) 330 m/s 
C) 300 m/s 
D) 390 m/s 
E) 470 m/s

Question 16

Suppose the wavelength of the 656.3-nm line in the hydrogen spectrum is shifted to 656.8 nm for light from a particular star.What can you deduce for the speed of the star relative to us?

Accepted Answer

A) 914 km/s toward us 
B) 457 km/s toward us 
C) 914 km/s away from us 
D) none of these answers 
E) 457 km/s away from us 
A) 914 km/s toward us 
B) 457 km/s toward us 
C) 914 km/s away from us 
D) none of these answers 
E) 457 km/s away from us

Question 17

Waves of amplitude 1.1 cm and wavelength 40 cm move along a 12-m long string that has a mass of 70 g and is under a tension of 15 N.Calculate the velocity of the wave.

Accepted Answer

A) 51 m/s 
B) 2570 m/s 
C) 16 m/s 
D) 15 m/s 
E) 331 m/s 
A) 51 m/s 
B) 2570 m/s 
C) 16 m/s 
D) 15 m/s 
E) 331 m/s

Question 18

The intensity of a certain spherical wave is 8.0 W/m2 at a distance of 1.0 m from the source.If the medium is isotropic and nonabsorbing,the intensity 100 m from the source is

Accepted Answer

A) 8.0 W/m2  
B) 6.4 $\times$ 10-4 W/m2  
C) 1.9 $\times$ 10-4 W/m2  
D) 8.0 $\times$ 10-4 W/m2  
E) 1.9 $\times$ 10-6 W/m2  
A) 8.0 W/m2  
B) 6.4 $\times$ 10-4 W/m2  
C) 1.9 $\times$ 10-4 W/m2  
D) 8.0 $\times$ 10-4 W/m2  
E) 1.9 $\times$ 10-6 W/m2

Question 19

If a sound of intensity I = 1.0 F1F1F1S1F1F1F10 10-6 W/m2 falls on a detector of area A = 7.0 $\times$ 10-5 m2 (about the size of your eardrum),how much power is received by the detector?

Accepted Answer

A) 6.2 $\times$ 10-14 W 
B) 1.0 $\times$ 10-6 W 
C) 7.0 $\times$ 10-11 W 
D) 1.4 $\times$ 10-2 W 
E) 70 W 
A) 6.2 $\times$ 10-14 W 
B) 1.0 $\times$ 10-6 W 
C) 7.0 $\times$ 10-11 W 
D) 1.4 $\times$ 10-2 W 
E) 70 W

Question 20

Two sounds differ by 30 dB.The intensity of the louder sound IL,compared with the softer IS,is IL/IS.The value of the ratio is

Accepted Answer

A) 1000 
B) 30 
C) 9 
D) 100 
E) 300 
A) 1000 
B) 30 
C) 9 
D) 100 
E) 300

Exam 15: Wave Motion

The human ear can be sensitive to sound frequencies up to 20 kHz.What wavelength does this correspond to at normal temperature and pressure?

The intensity of a wave at a certain point is I.A second wave has twice the energy density and three times the speed of the first.What is the intensity of the second wave?

An oscillator tuned to a frequency of 1 kHz is dropped from a tall building.How does the frequency picked up by a stationary observer at the top of the building change with time?

The frequency of a car horn is f.What frequency is observed if both the car and the observer are at rest,but a wind is blowing toward the observer?

Workmen are digging up the road using pneumatic tools.If a single tool creates a noise level of 88 decibels a few meters away,calculate the noise level if four such tools were in operation the same distance away.

A sinusoidal wave train is moving along a string.The equation giving the displacement y of a point at coordinate x has the form where the units are SI.The wavelength is

The sound level of a dog's bark is 50 dB.The intensity of a rock concert is 10,000 times that of the dog's bark.What is the sound level of the rock concert?

A jet engine emits a whine of frequency 3000 Hz.When the engine is moving directly away from an observer at half the speed of sound,an observer hears a frequency of

The power transmitted by any harmonic wave varies directly as

Which of the following statements about longitudinal and transverse pressure waves is NOT true?

If you were to double the amplitude and halve the frequency of a wave on a string while keeping the amplitude of the wave constant,the rate at which energy is delivered by the wave would

The picture on the right represents the wavefronts of a supersonic flight.The angle θ\thetaθ = 40 ∘\circ∘ .If the speed of sound is 300 m/s,what is the speed of the plane?

Suppose the wavelength of the 656.3-nm line in the hydrogen spectrum is shifted to 656.8 nm for light from a particular star.What can you deduce for the speed of the star relative to us?

Waves of amplitude 1.1 cm and wavelength 40 cm move along a 12-m long string that has a mass of 70 g and is under a tension of 15 N.Calculate the velocity of the wave.

The intensity of a certain spherical wave is 8.0 W/m2 at a distance of 1.0 m from the source.If the medium is isotropic and nonabsorbing,the intensity 100 m from the source is

If a sound of intensity I = 1.0  10-6 W/m2 falls on a detector of area A = 7.0 ×\times× 10-5 m2 (about the size of your eardrum),how much power is received by the detector?

Two sounds differ by 30 dB.The intensity of the louder sound IL,compared with the softer IS,is IL/IS.The value of the ratio is

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The intensity of a certain spherical wave is 8.0 W/m² at a distance of 1.0 m from the source.If the medium is isotropic and nonabsorbing,the intensity 100 m from the source is

If a sound of intensity I = 1.0  10^-6 W/m² falls on a detector of area A = 7.0 $\times$ 10^-5 m² (about the size of your eardrum),how much power is received by the detector?

Two sounds differ by 30 dB.The intensity of the louder sound I_L,compared with the softer I_S,is I_L/I_S.The value of the ratio is