# Honors Physics I chapter 12: Sound 2013-2014 Exam Multiple Choice

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Honors Physics I - Chapter 12: Sound 2013-2014 Exam
Multiple Choice

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

1. Sound waves
 a. are a part of the electromagnetic spectrum. b. do not require a medium for transmission. c. are longitudinal waves. d. are transverse waves.

2. Of the following materials, sound waves travel fastest through

 a. helium at 0°C. b. air at 0°C. c. copper at 0°C. d. air at 100°C.

3. In general, sound travels faster through

 a. solids than through gases. b. gases than through solids. c. gases than through liquids. d. empty space than through matter.

4. At a large distance from a sound source, spherical wave fronts are viewed as

 a. wavelengths. b. troughs. c. rays. d. plane waves.

5. The distance between wave fronts of plane waves corresponds to ____ of a sound wave.

 a. one wavelength b. two amplitudes c. one compression d. two rarefactions

6. The Doppler effect occurs with

 a. only sound waves. b. only transverse waves. c. only water waves. d. all waves.

7. When an air column vibrates in a pipe that is open at both ends,

 a. all harmonics are present. b. no harmonics are present. c. only odd harmonics are present. d. only even harmonics are present.

8. When an air column vibrates in a pipe that is closed at one end,

 a. all harmonics are present. b. no harmonics are present. c. only odd harmonics are present. d. only even harmonics are present.

9. How many beats per second are heard when two vibrating tuning forks having frequencies of 342 Hz and 345 Hz are held side by side?

 a. 687 Hz b. 343.5 Hz c. 5 Hz d. 3 Hz

10. Audible beats are formed by the interference of two waves

 a. of slightly different frequencies. b. of greatly different frequencies. c. with equal frequencies, but traveling in opposite directions. d. from the same vibrating source.

11. The human perception of pitch depends on a sound’s

 a. velocity. b. wavelength. c. frequency. d. amplitude.

12. Spherical wave fronts can be treated as parallel lines when

 a. they are very near the source. b. the frequency is very high. c. the wavelength is very large. d. they are a large distance from the source.

13. When the measured intensity of a sound increases from 1.0 ´ 10–4 to 1.0 ´ 10–3, the decibel level increases from 80 dB to

 a. 800 dB. b. 100 dB. c. 90 dB. d. 70 dB.

14. Resonance occurs when a force causes an object to vibrate at

 a. a large amplitude. b. a low pitch. c. any frequency. d. its natural frequency.

15. Two flute players are tuning their instruments. One player sounds a tone with a pitch of 527 Hz and the other player sounds a tone with a pitch of 523 Hz. How many beats per second will the players hear?

 a. none b. 2 c. 4 d. 525

16. At a large distance from a sound source, spherical wave fronts are viewed as

 a. wavelengths. b. troughs. c. rays. d. plane waves.

17. The distance between wave fronts of plane waves corresponds to _________ of a sound wave.

 a. one wavelength b. two amplitudes c. one compression d. one rarefaction

18. The property of sound called intensity is proportional to the rate at which energy flows through

 a. an area perpendicular to the direction of propagation. b. an area parallel to the direction of propagation. c. a cylindrical tube. d. a sound wave of a certain frequency.

19. A sound twice the intensity of the faintest audible sound is not perceived as twice as loud because the sensation of loudness in human hearing

 a. is approximately logarithmic. b. is approximately exponential. c. depends on the speed of sound. d. is proportional to frequency.

20. When an air column vibrates in a pipe that is open at both ends,

 a. all harmonics are present. b. no harmonics are present. c. only odd harmonics are present. d. only even harmonics are present.

21. When an air column vibrates in a pipe that is closed at one end,

 a. all harmonics are present. b. no harmonics are present. c. only odd harmonics are present. d. only even harmonics are present.

22. A train moves down the track toward an observer. The sound from the train, as heard by the observer, is ___ the sound heard by a passenger on the train.

 a. the same as b. a different timbre than c. higher in pitch than d. lower in pitch than

23. If you are on a train, how will the pitch of the train’s whistle sound to you as the train moves?

 a. The pitch will become steadily higher. b. The pitch will become steadily lower. c. The pitch will not change. d. The pitch will become higher, and then become lower.

24. If the intensity of a sound is increased by a factor of 100, the new decibel level will increase

 a. by two units. b. to twice the old one. c. by a factor of 10. d. by 20 units.

25.

In the figure shown above, a beat occurs at

 a. t1. b. t2. c. t3. d. t1 and t3.

Problem

1. A wave on a guitar string has a velocity of 626 m/s. The guitar string is 67.4 cm long. What is the fundamental frequency of the vibrating string?
2. A resonating glass tube closed at one end is 3.6 cm wide and 31.2 cm long. What are the frequencies of the first two harmonics for the resonating tube? The speed of sound in air at this temperature is 351 m/s.
3. Closed-end organ pipes often have a movable closure that can be adjusted up or down to tune the pipe to the desired pitch. The resonant length of a certain closed-end pipe is 27.2 cm. By how many centimeters must this pipe be shortened or lengthened in order to tune it to a fundamental frequency of 342 Hz? The pipe is in an environment in which the speed of sound is 341 m/s.
4. What is the intensity of sound waves produced by a trumpet at a distance of 1.6 m when the power output of the trumpet is 0.30 W?
5. What length of guitar string would vibrate at a fundamental frequency of 825 Hz if the string is stretched so that the velocity of waves on the string is 577 m/s

?

Honors Physics I - Chapter 12: Sound 2013-2014 Exam

MULTIPLE CHOICE
1. ANS: C PTS: 1 DIF: I OBJ: 12-1.1
2. ANS: C PTS: 1 DIF: II OBJ: 12-1.3
3. ANS: A PTS: 1 DIF: I OBJ: 12-1.3
4. ANS: D PTS: 1 DIF: I OBJ: 12-1.4
5. ANS: A PTS: 1 DIF: II OBJ: 12-1.4
6. ANS: D PTS: 1 DIF: I OBJ: 12-1.5
7. ANS: A PTS: 1 DIF: I OBJ: 12-3.1
8. ANS: C PTS: 1 DIF: I OBJ: 12-3.1
9. ANS: D PTS: 1 DIF: IIIA OBJ: 12-3.4
10. ANS: A PTS: 1 DIF: I OBJ: 12-3.4
11. ANS: C PTS: 1 TOP: Chapter 12 Section Quiz 1
12. ANS: D PTS: 1 TOP: Chapter 12 Section Quiz 1
13. ANS: C PTS: 1 TOP: Chapter 12 Section Quiz 2
14. ANS: D PTS: 1 TOP: Chapter 12 Section Quiz 2
15. ANS: C PTS: 1 TOP: Chapter 12 Section Quiz 3
16. ANS: D PTS: 1 TOP: Chapter 12 Test A
17. ANS: A PTS: 1 TOP: Chapter 12 Test A
18. ANS: A PTS: 1 TOP: Chapter 12 Test A
19. ANS: A PTS: 1 TOP: Chapter 12 Test A
20. ANS: A PTS: 1 TOP: Chapter 12 Test A
21. ANS: C PTS: 1 TOP: Chapter 12 Test A
22. ANS: C PTS: 1 TOP: Chapter 12 Test B
23. ANS: C PTS: 1 TOP: Chapter 12 Test B
24. ANS: D PTS: 1 TOP: Chapter 12 Test B
25. ANS: B PTS: 1 TOP: Chapter 12 Test B
PROBLEM
1. ANS:

464 Hz
Given

Solution

At the fundamental frequency (first harmonic), n = 1, so

PTS: 1 DIF: IIIA OBJ: 12-3.2

2. ANS:

281 Hz, 843 Hz

Given

v 351 m/s

L 31.2 cm 0.312 m
Solution

For a resonating tube closed at one end,

At the fundamental frequency (first harmonic), n = 1, so

The next harmonic in a closed pipe is the third, where n = 3.

PTS: 1 DIF: IIIB OBJ: 12-3.2

3. ANS:

The resonant length must be shortened by 2.3 cm to 24.9 cm.

Given

v 341 m/s

f 342 Hz

L 27.2 cm
Solution

L

change in length L L

PTS: 1 DIF: IIIC OBJ: 12-3.2
4. ANS:

9.3 1023 W/m2

Given

P = 0.30 W

r = 1.6 m

Solution

Intensity =

Intensity = = 9.3 1023 W/m2

PTS: 1 TOP: Chapter 12 Test B

5. ANS:

0.350 m

Given

v = 577 m/s

f1 = 825 Hz

Solution

fl =

L = = = 0.350 m

PTS: 1 TOP: Chapter 12 Test B