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Name: ________________________ Class: ___________________ Date: __________ ID: A

Unit 4 Sound and Waves

Multiple Choice

Identify the choice that best completes the statement or answers the question.

____ 1. The speed of any mechanical wave as it propagates through a medium is dependent mainly on the a.

b.

c.

d.

e.

frequency of the wave source wavelength period of the wave type of medium through which the wave travels amplitude ____ 2. The shortest time interval in which a wave motion completely repeats itself (i.e., makes one complete vibration or oscillation) is called the a.

amplitude b.

c.

period wavelength d.

e.

frequency speed ____ 3. A transverse wave has an amplitude of 2.4 m. What is the vertical distance, in metres, between the top of a crest and the bottom of a trough?

a.

b.

0.60

1.2

d.

e.

3.6

4.8

c.

2.4

____ 4. Which point, shown in the diagram below, is in phase with point C?

a.

b.

c.

B D E d.

e.

F G ____ 5. In a longitudinal wave, a.

The particles move parallel to the direction of the wave motion.

b.

c.

The particles move perpendicular to the direction of the wave motion.

Energy causes the particles to move forward with the wave.

d.

e.

Energy is propagated by crests and troughs.

The speed is unaffected by the type of medium used.

____ 6. In an ideal wave, which of the following wave properties does not change as it travels along the same medium?

a.

amplitude b.

c.

wavelength frequency d.

e.

period all of the above 4

Name: ________________________ ID: A

____ 7. Consider the following wave properties: (i) speed (ii) (iii) (iv) frequency wavelength period ____ Which of the above quantities does not change as a wave changes mediums?

a.

(i) only d.

(i) and (iv) only b.

c.

(ii) only (i) and (iii) only e.

(ii) and (iv) only 8. A water wave travels from shallow water to deep water and speeds up. Which of the following statements best describes the wave's behaviour as it changes mediums?

a.

b.

The wavelength is shorter in the shallow water and longer in the deeper water.

The wavelength is longer in the shallow water and shorter in the deeper water.

c.

d.

e.

The wavelength is unaffected.

The frequency of the wave is lower in the shallow water and higher in the deeper water.

The frequency of the wave is higher in the shallow water and lower in the deeper water.

____ 9. What will occur when the two pulses, shown below, interfere with each other?

a.

b.

c.

d.

e.

A node is created, then the pulses will continue to travel on unaffected.

A super crest is created, then the pulses will continue to travel on unaffected.

A node is created, then the pulses bounce off each other and return to their starting points.

The two pulses completely destroy each other and they disappear.

The two pulses join to form a new crest and travel to the left together.

____ 10. Which wave property most affects the intensity or loudness of sound?

a.

reflection d.

amplitude b.

c.

complexity frequency e.

speed ____ 11. Which of the following frequencies is ultrasonic?

a.

b.

c.

12 Hz 25 Hz 332 Hz d.

e.

5000 Hz 25 000 Hz ____ 12. The change in direction of a sound wave around corners is called a.

diffraction d.

interference b.

refraction e.

resonance c.

reflection 2

Name: ________________________ ID: A

____ 13. An ambulance is approaching a stationary observer. For the observer, the apparent frequency of the siren compared to the actual frequency of the siren a.

increases or decreases depending on the speed of the ambulance b.

c.

d.

e.

resonates decreases stays the same increases ____ 14. One sound source has an intensity of 40 dB, while another has an intensity of 70 dB. The intensity of these two differs by a factor of a.

b.

c.

3 30 1000 d.

e.

2800 10 30 ____ 15. Which of the following frequencies is infrasonic?

a.

12 Hz d.

b.

c.

25 Hz 332 Hz e.

5000 Hz 25 000 Hz ____ 16. Which of the following intensities is 100 times greater than 10 dB?

a.

–90 dB d.

110 dB b.

c.

0 dB 30 dB e.

1000 dB ____ 17. The frequency of a sound wave is 50 Hz. What is its period?

a.

0.20 s d.

0.020 m/s b.

c.

0.020 s 0.020 Hz e.

50 s ____ 18. During constructive interference in sound, which of the following could be produced?

a.

louder sound d.

resonance b.

c.

node quieter sound e.

supercrest ____ 19. When measuring the speed of sound outdoors, it is generally a.

fastest in the spring d.

fastest in the winter b.

c.

fastest in the summer fastest in the autumn e.

the same for all seasons ____ 20. Scientifically, noise is best described as a.

sounds that are unpleasant to humans b.

c.

d.

e.

the background hiss often heard on old recordings sound that originates from a source where the frequencies are not constant sound that originates from a source where only one frequency is produced the presence of three or more constant frequencies ____ 21. Waves that are produced on a guitar string by plucking it are a.

sound waves d.

acoustic waves b.

longitudinal waves e.

transverse waves c.

electromagnetic waves 3

Name: ________________________ ID: A Short Answer

22. State the type of vibration that occurs in each of the following: (a) the spring in a pogo stick as a child bounces up and down on it (b) a tree swaying in the wind (c) the rotating masses on an anniversary clock 23. When playing a stereo, there are certain sounds that can cause windows to rattle. Explain why this occurs.

24. For each of the following, calculate the frequency, in hertz, and the period, in seconds: (a) a bee beating its wings 3000 times in 30 s (b) a tuning fork completing 2048 oscillations in 8.0 s 25. For each of the following, calculate the frequency, in hertz, and the period, in seconds: (a) a pendulum swinging 20 times per minute (b) a car engine rotating at 8000 rpm's (revolutions per minute) 26. Sketch the resultant wave form when the following two pulses meet. (Assume the meeting point corresponds to the centre of each pulse.) 27. Explain, briefly, why you can hear someone around a corner even though you cannot see them.

28. The engine of a Grand Prix race car sounds different as it approaches you than when it is moving away from you. Explain why.

Problem

29. Calculate the period and frequency of a pendulum that completes 150 vibrations in 1.5 min.

30. A sound wave with a frequency of 1.25  10 4 Hz travels at 344 m/s. What is its wavelength?

4

Unit 4 Sound and Waves Answer Section

MULTIPLE CHOICE

STA: WS1.02

STA: WS1.01

STA: WS1.01

STA: WS1.01

STA: WS1.02

STA: WS1.02

STA: WS2.01

STA: WS2.01

STA: WS1.04

STA: WS3.01

STA: WS3.01

STA: WS2.01

STA: WS1.07

STA: WS1.01

STA: WS3.01

STA: WS1.01

STA: WS1.01

STA: WS2.01

STA: WS1.03

STA: WS3.03

1

ID: A

STA: WS1.02

SHORT ANSWER ID: A

(a) longitudinal (b) transverse (c) torsional PTS: 1 REF: MC OBJ: 6.1 STA: WS1.01

The stereo is creating sound waves that have the same natural frequency as the windows in the car. This causes sympathetic vibrations to start in the windows and makes them rattle. This effect is due to resonance.

PTS: 1 REF: MC OBJ: 6.7 STA: WS1.05

For each solution, the following formulas were used: frequency (Hz)  number of cycles time interval (s) period (s)  1 frequency (Hz) (a) frequency = 100 Hz, period = 0.010 s (b) frequency = 256 Hz, period = 0.0039 s PTS: 1 REF: C OBJ: 6.1 For each solution, the following formulas were used: frequency (Hz)  number of cycles time interval (s) period (s)  1 frequency (Hz) (a) frequency = 0.33 Hz, period = 3.0 s (b) frequency = 133 Hz, period = 0.0075 s PTS: 1 REF: C OBJ: 6.1 STA: WS1.01

STA: WS1.01

2

Use the principle of superposition.

ID: A

PTS: 1 REF: K/U OBJ: 6.6 STA: WS1.04

Waves can travel around corners due to a property called diffraction. Diffraction describes the ability of a wave to bend as it travels through small openings, around corners, or around objects. This allows the sound wave to bend as it travels past a corner allowing you to hear the person speaking even though you cannot see them.

PTS: 1 REF: C OBJ: 7.7 STA: WS2.01

Since the car is moving relative to you, the sound it makes is subject to the Doppler effect. As the car approaches, its engine produces a sound with a higher apparent frequency than when the car is moving away, so the pitch appears to change as the car races past you.

PTS: 1 REF: C OBJ: 7.10 STA: WS1.07

3

PROBLEM

ANS:

N

 150 vibrations

t

 1.5 min  90 s

T

 ?

f

 ?

T

t N

 90 s 150 vibrations  0.60 s

f

 1

T

 1 0.60 s  1.6667 Hz

The period is 0.60 s and the frequency is 1.7 Hz.

OBJ: 6.1 PTS: 1 REF: K/U

f

 1.25

 10 4 Hz

v

 344 m/s   ?

v

f

  

v f

 344 m/s 1.25

 10 4 Hz  0.02752 m

The wavelength is 2.75

10

–2

m.

PTS: 1 REF: C OBJ: 6.3 STA: WS1.01

STA: WS1.02

4

ID: A

Unit 4 Sound and Waves [Answer Strip] ID: A

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