# Quiz 14: Waves

Physics & Astronomy

Q 1Q 1

Which of these statements can be correctly applied to a wave?
A)Its motion results in the flow of material.
B)Its motion in a medium transfers mass and energy.
C)Its motion in a medium transfers energy.
D)They all require a medium in which to propagate.

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Multiple Choice

C

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Multiple Choice

C

Q 3Q 3

If the speed of a wave increases, how would one of these other parameters change?
A)wavelength increases
B)period increases
C)frequency decreases
D)amplitude increases

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Multiple Choice

A

Q 4Q 4

The vibration of a piano's A-string produces a wave with a wavelength of ë = 78 cm, and propagates with a speed of 343 m/s. What is the frequency?
A)0.44 Hz
B)4.40 Hz
C)44.0 Hz
D)440 Hz

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Multiple Choice

Q 5Q 5

Which of the following equations represents a wave function moving to the left (-x-direction)?
A)y(x, t) = x - 4.0t
B)y(x, t) = (-20.0t + x)

^{2}C)y(x, t) = x + 4.0t D)y(x, t) = (x - 2.0t)^{2}Free

Multiple Choice

Q 6Q 6

Which of the following equations represents a wave function moving to the right (+x-direction)?
A)y(x, t) = x + 4.0t
B)y(x, t) = (20.0t + x)

^{2}C)y(x, t) = x - 4.0t D)y(x, t) = (x + 2.0t)^{2}Free

Multiple Choice

Q 7Q 7

Figure 14.1
The figure shows a wave.
-If L

_{2}= 65.5 cm, which note from Table 14.1 is represented in Fig. 14.1? Assume that the speed of sound is 343 m/s. A)G3 B)C4 C)G4 D)C5Free

Multiple Choice

Q 8Q 8

Figure 14.1
The figure shows a wave.
-The wave from Fig. 14.1 is moving at a speed of 5 cm/s. If L

_{1}= 6 cm and L_{2}= 5 cm, which wave equation describes the wave? A)y(x, t) = (6 cm)sin[(6.28 s^{-1})t - (1.05 cm^{-1})x)] B)y(x, t) = (3 cm)sin[(12.6 s^{-1})t - (0.63 cm^{-1})x)] C)y(x, t) = (3 cm)sin[(6.28 s^{-1})t - (1.05 cm^{-1})x)] D)y(x, t) = (6 cm)sin[(3.76 s^{-1})t - (2.09 cm^{-1})x)]Free

Multiple Choice

Q 9Q 9

Figure 14.2 The figure shows a wave in a rope with two points labelled A and B.
-A harmonic wave is travelling to the right on a long, stretched rope. Two points on the rope are labelled A and B (see Fig. 14.2). When the wave moves a little to the right, how do these two points move?
A)Both A and B move to the right.
B)Point A moves to the right and B to the left.
C)Point A moves down and B up.
D)Point A moves up and B down.

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Multiple Choice

Q 10Q 10

Figure 14.2 The figure shows a wave in a rope with two points labelled A and B.
-A harmonic wave travelling along the x-axis is described by the equation y(x, t) = (4 cm)sin[(0.5 cm)x - (1.05 s

^{-1})t)]. What is the wavelength of the wave? A)0.5 cm B)1.05 cm C)4.0 cm D)12.6 cmFree

Multiple Choice

Q 11Q 11

Figure 14.3 The figure shows two waves.
-What is the phase difference, ÄÖ, between the two waves in Fig. 14.3?
A)2ð
B)3ð/2
C)ð
D)ð/2

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Multiple Choice

Q 12Q 12

Figure 14.3 The figure shows two waves.
-What additional phase difference between the waves in Fig. 14.3 would be needed for the interference of the two waves to be destructive?
A)2ð
B)3ð/2
C)ð
D)ð/2

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Multiple Choice

Q 13Q 13

Figure 14.3 The figure shows two waves.
-Two identical waves are in interference. The resultant amplitude will be zero if the phase difference between the waves is __________.
A)2ð
B)ð
C)ð/2
D)ð/4

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Multiple Choice

Q 14Q 14

Which of these waves can experience interference?
A)only sinusoidal waves
B)only longitudinal waves
C)only electromagnetic waves
D)all types of waves

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Multiple Choice

Q 15Q 15

A wave on a string is represented by the wave function y(x, t) = Asin(kx - ùt). When it reflects at a loose end, what is the wave function of the reflected wave?
A)y(x, t) = Asin(kx - ùt)
B)y(x, t) = -Asin(kx + ùt)
C)y(x, t) = Asin(kx + ùt)
D)y(x, t) = -Asin(kx - ùt)

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Multiple Choice

Q 16Q 16

Two ropes, A and B, are tied and stretched. Rope A has a linear mass density 9 times higher than rope B. A pulse travels in rope A and continues in B. The speed of the pulse in rope A is v

_{A}, and in rope B it is v_{B}. What is the relationship between the speeds? A)v_{B}= 9v_{A}B)v_{B}= 3v_{A}C)v_{A}= 9v_{B}D)v_{A}= 3v_{B}Free

Multiple Choice

Q 17Q 17

String with fixed ends can vibrate in several modes (harmonics). How does the length of a string relate to wavelengths of harmonics?
A)The length of a string contains an integer number of full wavelengths.
B)The length of a string contains an integer number of half wavelengths.
C)The length of a string contains only an odd number of full wavelengths.
D)The length of a string contains only an odd number of half wavelengths.

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Multiple Choice

Q 18Q 18

A string is under tension. You release the tension to half its previous value. The frequency of the first harmonic
A)decreases by a factor of .
B)increases by factor of 2.
C)does not change, but wavelength reduces to half.
D)decreases by a factor of 4.

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Multiple Choice

Q 19Q 19

Figure 14.4 Fig. 14.4 shows a standing wave.
-A cello C-string vibrates in its fundamental mode with a frequency of 65 Hz. What is the frequency of the harmonic in Fig. 14.4?
A)22 Hz
B)130 Hz
C)195 Hz
D)260 Hz

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Multiple Choice

Q 20Q 20

See Fig. 14.4. For a typical high E guitar string with frequency f = 329.6 Hz, what is the ratio between the tensions when it is tuned to the fundamental tone, T

_{f}, and when it is tuned to harmonic, T_{h}? A)1/3 B)1/ C) D)3Free

Multiple Choice

Q 21Q 21

When a wave passes through a certain medium, the particles of the medium move with the wave. For example, a sound wave propagates through air via air molecules that move from the source to receiver.

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True False

Q 22Q 22

When a wave passes through a certain medium, the particles of the medium move with the wave. For example, a sound wave propagates through air via air molecules, which move from the source to receiver.

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True False

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True False

Q 24Q 24

The frequency of a wave is determined by the source of the wave, but wavelength is not. Wavelength depends on the medium through which the wave propagates.

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True False

Q 25Q 25

The wave described by the equation y(x, t) = (4 cm)sin[(0.5 cm)x + (1.05 s

^{-1})t)] is moving along the x-axis in the positive direction (to the right).Free

True False

Q 26Q 26

If we add two sine waves at the same point in space, the resultant has to have a larger amplitude than either of individual waves.

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True False

Q 27Q 27

Constructive interference occurs only when two harmonious waves arrive at the same point with a phase difference of exactly 1 wavelength.

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True False

Q 28Q 28

A reflected wave on a fixed end is inverted, but does not change shape. A reflected wave on a loose end is not inverted, nor does it change shape.

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True False

Q 29Q 29

Whenever a wave reflects off the boundary between denser and less dense medium, in any direction, it will result in an inverted wave.

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True False

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True False

Q 31Q 31

An antenna 72.8 m long has a length equal to ¼ of a wavelength of the produced wave. If the station using this antenna emits a signal of 1030 kHz, what is the speed of the wave?

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Short Answer

Q 32Q 32

Bats use ultrasound to locate prey. The wavelength of sound has to be of the order of size of the prey if the prey is to be detected. What is the size of the smallest insect a bat can detect if it emits a sound at 55 kHz? The speed of sound is 343 m/s.

Free

Essay

Q 33Q 33

Figure 14.5
Fig. 14.5 shows a sound wave.
-Fig. 14.5 shows a sound wave in the air. L

_{1}= 200 ìPa, L_{2}= 52.4 cm. Which note from Table 14.1 is represented? What is the amplitude of the wave? Take the speed of sound in the air as 343 m/s.Free

Essay

Q 34Q 34

Figure 14.5
Fig. 14.5 shows a sound wave.
-Fig. 14.5 shows a sound wave in the water. L

_{1}= 220 ìPa, L_{2}= 226 cm. Which note from Table 14.1 is represented? What is the amplitude of the wave? Take the speed of sound in the water as 1482 m/s.Free

Essay

Q 35Q 35

Which note is represented by the wave equation y(x, t) = 2sin[(1642 s

^{-1})t - (4.79 m^{-1})x? For reference, use Table 14.1.Free

Short Answer

Q 36Q 36

Figure 14.6 Fig. 14.6 shows a sound wave.
-What is the amplitude of the wave represented in Fig. 14.6? What are the wavelength and the frequency, assuming that it is a sound wave in air? The speed of sound in air is 343 m/s.

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Short Answer

Q 37Q 37

Figure 14.6 Fig. 14.6 shows a sound wave.
-What is the amplitude of the wave represented in Fig. 14.6? What are the wavelength and the frequency, assuming that it is a radio wave? The speed of the radio wave is 3 × 10

^{8}m/s.Free

Short Answer

Q 38Q 38

Two identical waves (having the same wavelength and amplitude) interfere with each other. The initial amplitude of each wave was 28 cm; the resultant wave has an amplitude of 12 cm. What is the phase difference between the waves represented as a fraction of a wavelength?

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Essay

Q 39Q 39

Describe the difference between reflected waves in these two cases: when the incident wave propagates from a less dense medium to a denser medium, and the opposite case, when the incident wave propagates from a denser medium to a less dense medium.

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Essay

Q 40Q 40

A cello C-string vibrates in its fundamental mode with a frequency of 60 Hz. In order to tune it to a proper frequency of 65 Hz, how do you adjust the tension?

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Essay