PHY1
Review for Exam 10
Topics
1. Sound
a. Longitudinal waves
b. Pitch and frequency
c. Speed of sound
d. Doppler Effect
e. Loudness and Decibels
f. Interference/beats
2. Music
a. Octaves
b.
c.
d.
e.
Fundamentals and overtones
String instruments
Open tubes
Closed tubes
Equations
v=fλ
f = 1/T
v = B/p
v = [Ft/(m/L)]1/2
v = 331 + 0.6T
β = 10 log [I/Io]
Multiple Choice Questions
1. What is the speed of sound in air on
a hot day, 30°C?
(1) 3.31 x 102 m/s
(2) 3.43 x 102 m/s
(3) 3.49 x 102 m/s
(4) 3.00 x 108 m/s
2. Middle C on a piano has a frequency
of 262 Hertz. What is the frequency
of the C that is one octave above
middle C?
(1) 131 Hz
(3) 393 Hz
(2) 262 Hz
(4) 524 Hz
3. What is the length of a piano string
that produces a frequency of 262 Hz
and in which the speed of the sound
wave is 262 m/s
(1) 0.5 m
(3) 1.5 m
(2) 1.0 m
(4) 2.0 m
4. A vibrating closed tube resonator
produces a fundamental resonance
when a tuning fork is held over the
top of the tube. How long would the
column of air have to be to produce
resonance for the first overtone?
(1) ¼ λ
(3) ½ λ
(2) ¾ λ
(4) λ
5. A loud speaker is creating a single
frequency sound. If a person moves
away from the speaker and then
stops. The frequency of the sound is
(1) The same as when the person was
closer to the speaker.
(2) Higher than when the person was
closer to the speaker.
(3) Lower than when the person was
closer to the speaker.
6. A stationary person is 100. m away
from another stationary person on a
day when the temperature is 20° C.
How long does it take for a sound
spoken by the first person to reach
the second person?
(1) 1.0 s
(3) 3.4 x 104 s
(2) 0.29 s
(4) 3.43 s
PHY1
Review for Exam 10
7. Two tuning forks are struck and
listened to simultaneously, producing
a beat frequency of 4.0 Hz. If one of
the tuning forks is known to produce
a 440 Hz note, which of the
following is a possible frequency of
the second tuning fork?
(1) 440 Hz
(3) 4 Hz
(2) 880 Hz
(4) 444 Hz
8. Which of the following musical
instruments is an example of a closed
tube resonator?
(1) pipe organ
(2) trumpet
(3) piano
(4) violin
9. Which of the following represents
the loudest sound?
(1) 262 Hz and 120 dB
(2) 330 Hz and 100 dB
(3) 415 Hz and 50 dB
(4) 440 Hz and 20 dB
10. What two properties of a material
determine the speed of sound in that
material?
(1) Refractive index and elastic
modulus
(2) Density and elastic modulus
(3) Refractive index and density
11. In an open tube resonator, the
standing wave created inside of the
tube must always meet which of the
following conditions?
(1) A node must be in the center of
the tube.
(2) An antinode must be in the center
of the tube.
(3) Antinodes must occur at the ends
of the tube.
(4) Nodes must occur at the ends of
the tube.
12. When a sound wave passes from air
into water, which of the following
does not change?
(1) speed
(3) wavelength
(2) frequency
(4) pitch
13. Which of the following properties of
sound are inversely related?
(1) speed and frequency
(2) speed and wavelength
(3) wavelength and frequency
14. What is the decibel level of a sound
that has an intensity of 1.0 W/m2, if
the threshold of hearing is 1.0 x 10-12
W/m2?
(1) 0 dB
(3) 120 dB
(2) 70 dB
(4) 140 dB
15. Which of the following notes has a
pitch higher than A# (466 Hz)
(1) G (392 Hz)
(3) B (494 Hz)
(2) D (277 Hz)
(4) C (262 Hz)
PHY1
Review for Exam 10
Short Answers
16. Briefly explain why not all of the strings of a piano are made of the same wire, with
the lower pitched notes being made by strings with a larger diameter than the higher
pitched notes.
17. What is the length of an organ pipe that emits middle C (262 Hz) when the
temperature is 21°C?
18. A person at a rock concert sits 20 meters from a loud speaker and experiences a sound
level of 110 dB.
(a) What is the intensity of the sound that her eardrums hear if the threshold level of
sound is 10-12 W/m2?
(b) If the average eardrum has a radius of 1.0 cm, what is the average power that the
eardrums experience?
PHY1
Review for Exam 10
19. A highway overpass was observed to resonate as one full loop when a small
earthquake shook the ground vertically at 4.0 Hz. The highway department put a
support at the center of the overpass, anchoring it to the ground. What resonate
frequency would you now expect for the overpass? Earthquakes rarely produce
frequencies that exceed 6 Hz. Was this modification an effective safeguard to prevent
the collapse of the bridge? Explain your answer and provide a drawing of the bridge
before and after the modification.
20. A sailor strikes the side of a ship just below the waterline. He hears the echo of the
sound reflected from the ocean floor directly below 2.0 s later. How deep is the
ocean below this ship if the sound travels through the seawater with a speed of 1440
m/s.