Deck 6: Waves and Sound

Question 1

When the frequency of the source of a water wave increases, the distance between successive peaks in the wave increases.

Answer 1

False

Question 2

The maximum displacement of points on a wave from the equilibrium position is the wave's wavelength.

Answer 2

False

Question 3

The wavelength of a wave divided by the frequency of the wave is the wave's speed.

Answer 3

False

Question 4

The distance between two successive 'like' points on a wave is the wave's wavelength.

Question 5

A sound wave in a metal bar is an example of a longitudinal wave.

Question 6

A source emits sound at a fixed constant frequency f .
If the source moves away from you, and at the same time you run away from the source, the frequency you hear is the same as f .

Question 7

A source emits sound at a fixed constant frequency f .
If the source moves away from you, the frequency you hear is lower than f .

Question 8

When a force F stretches a rope of mass per unit length ρ , the velocity of a wave in the rope is given by
You pull on a rope with a certain force, and a wave travels in the rope with a certain velocity. If you double your force, the velocity of a wave in the rope is now times the original velocity.

Question 9

Regions of a longitudinal wave where the particles of the medium are squeezed together are called compressions.

Question 10

Sound in a vacuum is impossible.

Question 11

When a force F stretches a rope of mass per unit length ρ , the velocity of a wave in the rope is given by
You have two identical ropes stretched with the same force between two different sets of posts. The second rope is twice as long as the first rope. The velocity of a wave in the second rope is half the velocity of a wave in the first rope.

Question 12

A source emits sound at a fixed constant frequency f .
If you run towards the source, the frequency you hear is lower than f .

Question 13

Waves carry energy.

Question 14

The speed of a wave is the same as the speed of the particles displaced by the wave.

Question 15

A water wave is an example of a transverse wave.

Question 16

When a force F stretches a rope of mass per unit length ρ , the velocity of a wave in the rope is given by
You have two ropes of the same length. The mass of the second rope is twice the mass of the first rope. The velocity of a wave in the second rope is times the velocity of a wave in the first rope.

Question 17

The number of cycles of a wave passing a point per unit time is the wave's period.

Question 18

The flash from a camera is an example of a continuous wave.

Question 19

When the frequency of the source of a water wave increases, the speed of the waves traveling in the water increases.

Question 20

A wave moves in a rope with a certain wavelength. A second wave is made to move in the same rope with twice the wavelength of the first wave. The frequency of the second wave is half the frequency of the first wave.

Question 21

Two identical sound producers will sound twice as loud as just one.

Question 22

Telephones don't transmit frequencies above 3,400 Hz. Musical notes should sound normal over the telephone as long as they are below 3,400 Hz.

Question 23

Combining two sounds of equal intensity will give a sound level 3 dB higher than the sound level due to just one of them.

Question 24

A source emits sound at a fixed constant frequency f .
If the source moves away from you faster than the speed of sound in air, you do not hear any frequency but instead a 'sonic boom.'

Question 25

As you move farther away from a source emitting a pure tone, the frequency of the sound you hear decreases.

Question 26

A source emits sound at a fixed constant frequency f .
If the temperature of the air rises, the frequency you hear is higher than f .

Question 27

Two uses of ultrasound are navigation by bats and controlling insects.

Question 28

A sound level of 80 dB has twenty times the amplitude of a 60 dB sound.

Question 29

Reverberation can both inhibit conversation and enhance music.

Question 30

Your vocal cords are used to produce all the sounds you make while speaking.

Question 31

Reverberation time of a room can be increased by covering the walls with better reflectors of sound.

Question 32

A sound with ten times the amplitude of another sound is judged to be ten times as loud.

Question 33

Two speakers in a stereo emit identical pure tones. As you move around in front of the speakers, you hear the sound alternating between loud and zero. This occurs because of diffraction.

Question 34

A zero decibel sound level has zero amplitude.

Question 35

You can hear sound through an open window from sources that are not in your line of sight because of diffraction.

Question 36

In order for two waves to interfere completely destructively, they must have the same amplitude.

Question 37

In ultrasound the wavelength of the sound is much smaller than in normal sound.

Question 38

Sound cannot travel through solid steel.

Question 39

If the source moves, the wavelength of the sound in front of the direction of motion is smaller than the wavelength behind the direction of motion.

Question 40

When two identical waves arrive at the same place in phase, there is destructive interference.

Question 41

Which of the following can change the frequency of a wave?

A) interference
B) the Doppler effect
C) diffraction
D) all of the above

Question 42

For waves moving through the atmosphere at a constant velocity, higher frequency waves must have proportionally longer wavelengths.

Question 43

The distance between two successive 'like' points on a wave is the wave's

A) speed.
B) frequency.
C) wavelength.
D) amplitude.
E) loudness.

Question 44

When a force F stretches a rope of mass per unit length ρ , the velocity of a wave in the rope is given by You pull on a rope with a certain force, and a wave travels in the rope with a certain velocity. If you double your force, the velocity of a wave in the rope is now ____________ the original velocity.

A) 1/2
B) times
C) the same as
D) times
E) 2 times

Question 45

Sound waves propagate in two dimensions.

Question 46

You drop a rock in a pond, and the water waves travel away from the rock with a certain speed. You drop a heavier rock in the water. The speed of the waves in the water from the heavier rock

A) remains unchanged.
B) increases.
C) decreases.
D) cannot be determined.

Question 47

When a force F stretches a rope of mass per unit length ρ , the velocity of a wave in the rope is given by You have two identical ropes stretched with the same force between two different sets of posts. The second rope is twice as long as the first rope. The velocity of a wave in the second rope is ____________ the velocity of a wave in the first rope.

A) 1/2
B)   times
C) the same as
D) times
E) 2 times

Question 48

When a force F stretches a rope of mass per unit length ρ , the velocity of a wave in the rope is given by You have two ropes of the same length. The mass of the second rope is twice the mass of the first rope. The velocity of a wave in the second rope is ___________ the velocity of a wave in the first rope.

A) 1/2
B) times
C) the same as
D) times
E) 2 times

Question 49

The distance between peaks on a wave divided by the time for the wave to travel this distance is the wave's

A) speed.
B) frequency.
C) wavelength.
D) amplitude.
E) loudness.

Question 50

The wavelength of a wave multiplied by the frequency of the wave is the wave's

A) speed.
B) frequency.
C) wavelength.
D) amplitude.
E) loudness.

Question 51

The number of cycles of a wave passing a point per unit time is the wave's

A) speed.
B) frequency.
C) wavelength.
D) amplitude.
E) loudness.

Question 52

If a source of sound is traveling toward you, the speed of the sound waves reaching you is _______________ the speed the sound waves would have had if the source were stationary.

A) faster than
B) slower than
C) the same as

Question 53

If you increase the linear mass density of a rope, the speed of a wave on the rope also increases.

Question 54

When the frequency of the source of a water wave increases, the distance between successive peaks in the wave

A) remains unchanged.
B) increases.
C) decreases.
D) cannot be determined.

Question 55

When the frequency of the source of a water wave increases, the speed of the waves traveling in the water

A) remains unchanged.
B) increases.
C) decreases.
D) cannot be determined.

Question 56

The maximum displacement of points on a wave from the equilibrium position is the wave's

A) speed.
B) frequency.
C) wavelength.
D) amplitude.
E) loudness.

Question 57

What is meant by a wave medium ?

A) a wave of moderate amplitude
B) water
C) air
D) any material through which a wave travels

Question 58

Two sound waves traveling through the air have different frequencies. Consequently, they must also have different

A) amplitudes.
B) speeds.
C) wavelengths.
D) all of the above

Question 59

In the troposphere segment of the Earth's atmosphere, as you increase in altitude the temperature decreases.  This means the speed of sound decreases as you increase in altitude.

Question 60

What is the symbol traditionally used to represent wavelength?

A) wl
B) y
C) μ
D) λ

Question 61

The wavelength of ultrasound at 1 million Hz in air where the speed of sound is 340 m/s is

A) 0.00000034 m.
B) 0.0000034 m.
C) 0.00034 m.
D) 0.34 m.
E) 340,000,000 m.

Question 62

A source emits sound at a fixed constant frequency f . If the source moves away from you faster than the speed of sound in air, the frequency that you hear is

A) the same as f.
B) higher than f.
C) lower than f.
D) unrelated to f.

Question 63

A source emits sound at a fixed constant frequency f . If you run towards the source, the frequency you hear is

A) the same as f.
B) higher than f.
C) lower than f.
D) unrelated to f.

Question 64

A source emits sound at a fixed constant frequency f . If the source moves away from you, and at the same time you run away from the source, the frequency you hear is

A) the same as f.
B) higher than f.
C) lower than f.
D) unrelated to f.

Question 65

Which of the following is not one of the ways sound can be used?

A) to circulate the refrigerant in a refrigerator
B) to relay information to orbiting satellites
C) to form images of internal organs
D) to measure the air temperature aloft
E) to make a bubble in water produce light

Question 66

Choose the correct statement.

A) The perceived pitch of a sound usually doesn't depend on the sound's frequency.
B) The frequency of each musical note is 10 Hz higher than that of the next lower note.
C) The decibel is the standard measure of tone quality.
D) The perceived loudness of a sound depends somewhat on frequency.

Question 67

As you move farther away from a source emitting a pure tone, the ___________ of the sound you hear decreases.

A) frequency
B) period
C) wavelength
D) amplitude
E) none of the above

Question 68

You listen to a live orchestra concert from a cheap seat far away, high up in the balcony. The music seems to be a little out of sync with the conductor's beat. Why?

A) The musicians are paying no attention to the conductor.
B) You are noticing a time lag due to the finite speed of sound.
C) The orchestra is not very good.
D) The viola section is dragging.

Question 69

The figure shows a 'snapshot' of four different waves in identical ropes stretched with the same force. The wave where the speed is greatest is

A) I.
B) II.
C) III.
D) IV.
E) all of the above.

Question 70

A source emits sound at a fixed constant frequency f . If the source moves away from you, the frequency you hear is

A) the same as f.
B) higher than f.
C) lower than f.
D) unrelated to f.

Question 71

In ultrasound the _____________ of the sound is much greater than in normal sound.

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

Question 72

Two speakers in a stereo emit identical pure tones. As you move around in front of the speakers, you hear the sound alternating between loud and zero. This occurs because of

A) interference.
B) changing sound level.
C) diffraction.
D) the Doppler effect.
E) shock waves.

Question 73

You can hear sound through an open window from sources that are not in your line of sight because of

A) interference.
B) diffraction.
C) the sound level.
D) the Doppler effect.
E) none of the above.

Question 74

A source emits sound at a fixed constant frequency f . If the temperature of the air rises, the frequency you hear is

A) the same as f.
B) higher than f.
C) lower than f.
D) unrelated to f.

Question 75

Which of these waves will diffract the most when passing through a 20 cm wide opening in a barrier?

A) a wave with a wavelength of 25 cm
B) a wave with a wavelength of 2 cm
C) a wave with a wavelength of 0.05 cm
D) none of these waves will diffract at all

Question 76

A wave moves in a rope with a certain wavelength. A second wave is made to move in the same rope with twice the wavelength of the first wave. The frequency of the second wave is _______________ the frequency of the first wave.

A) 1/2
B) the same as
C) 2 times
D) unrelated to

Question 77

When two identical waves arrive at the same place in phase, there is

A) constructive interference.
B) destructive interference.
C) diffraction.
D) a Doppler effect.
E) a shock wave.

Question 78

Ultrasound is used

A) to form images of internal organs.
B) by bats to navigate.
C) in automatic focus cameras.
D) to control insects.
E) all of the above

Question 79

A source emits sound at a fixed constant frequency f . If the source moves, the wavelength of the sound in front of the direction of motion is ____________ the wavelength behind the direction of motion.

A) the same as
B) larger than
C) smaller than
D) unrelated to

Question 80

You shout at a cliff, and hear your echo in 2 seconds. If the speed of sound in the air is 340 m/s, the distance of the cliff from you is

A) 85 m.
B) 170 m.
C) 340 m.
D) 680 m.
E) none of the above.