Physics 198
Exam 2
Fall 2014
Name_________________
Physics 198
Fall 2014
Exam 2
Thursday, October 30
Directions:
This 50-minute exam consists of twenty multiple-choice questions. This test is worth 20% of
your final grade. (The lowest score of three midterm exams will be dropped from the total
score.)
The questions on this test are not in order of difficulty.
You must mark all of your answers on both your test and answer sheet.
In marking the multiple choice bubble sheet use a number 2 pencil. Do not use ink. If you did
not bring a pencil, ask for one. Fill in the appropriate circles completely. If you need to change
any entry, you must completely erase your previous entry.
Carefully read each question and its five possible answers. Select one and only one answer for
each question. Choose the answer that is closest to the correct one.
When you are finished with the exam, return the bubble sheet and the exam itself.
Good luck!
Page 1 of 8
Physics 198
Exam 2
Fall 2014
21. The predominant frequency of a certain fire engine’s siren is 1550 Hz when at rest. What
frequency do you detect if you move with a speed of 30.0 m s toward the fire engine?
(Speed of sound: 340 m/s)
A)
B)
C)
D)
E)
1690 Hz
1580 Hz
1550 Hz
1520 Hz
1410 Hz
22. In order to obtain a good single slit diffraction pattern, the slit width could be:
A)
B)
C)
D)
E)
/100
/10

10
100
23. The Eustachian tube
A)
B)
C)
D)
E)
Connects the outer ear to the oral cavity
Connects the middle ear to the oral cavity
Connects the inner ear to the oral cavity
Connects the outer and middle ear
Connects the middle an inner ear
24. At low frequencies (below 1000 Hz) localization of sound is possible due to what factor?
A)
B)
C)
D)
E)
Time difference between sound traveling to two ears
The intensity difference at two ears (shadow effect)
Reflection from surrounding objects
Harmonics decomposition
Localization is impossible at these frequencies
25. According to the Fechner law sensation is what function of stimulus?
A)
B)
C)
D)
E)
Linear
Quadratic
Harmonic
Logarithmic
Exponential
Page 2 of 8
Physics 198
Exam 2
Fall 2014
26. What equation is correct?
A)
B)
C)
D)
E)
log( 400)  2  2 log 2
log( 400)  3  log 3
log( 400)  4  log 3
log( 400)  4 log 2
log( 400)  6 log 2
27. A source of a 500 Hz sound is operated at a power of 60 microwatts. The sound radiates
with equal intensity in all directions. What is the intensity level 50 m from the source?
A)
B)
C)
D)
E)
82 dB
70 dB
65 dB
41 dB
33 dB
28. Suppose that a single violin gives an average sound intensity level of 70 dB at a seat in the
audience. Now suppose that 2 violins play the same piece in the same way. What average
sound intensity level would you expect at the same seat in the audience?
A)
B)
C)
D)
E)
70 dB
73 dB
76 dB
79 dB
82 dB
29. Suppose that a single violin gives an average sound intensity level of 70 dB at a seat in the
audience that is L meters from the violin. What average sound intensity level would you
expect at a seat that is L/2 meters from the violin?
A)
B)
C)
D)
E)
70 dB
73 dB
76 dB
79 dB
82 dB
30. If two sounds differ by 20 dB, what is the ratio of their intensities?
A)
B)
C)
D)
E)
2
10
20
log20
100
Page 3 of 8
Physics 198
Exam 2
Fall 2014
31. What part of the ear is mainly responsible for critical band and for jnd (just-noticeable
difference)
A)
B)
C)
D)
E)
Outer ear
Middle ear
Eustachian tube
Basilar membrane
Semi-circular canals
32. What statement is wrong?
A)
B)
C)
D)
E)
Pitch increase with sound level for high frequencies
Pitch decrease with sound level for low frequencies
Pitch shows little changes for middle frequencies (~2000Hz)
Pitch decrease with sound level for high frequencies
Pitch depends on duration and on envelope of sound
33. What is virtual pitch?
A)
B)
C)
D)
E)
Second harmonic
Missing fundamental
The lowest frequency in the spectrum
The highest frequency in the spectrum
None of the above
34. Pure tones of 440 Hz and 600 Hz are sounded together. What is frequency of beats?
A)
B)
C)
D)
E)
600 Hz
440 Hz
160 Hz
80 Hz
None of the above
35. What frequency ratio gives an interval that is exactly 1/12 of an octave?
A)
B)
C)
D)
E)
1/6
1/7
1/12
21 12
21 6
Page 4 of 8
Physics 198
Exam 2
Fall 2014
36. What ratio has minor third in equal temperament?




4
A) 21 / 12  21 / 3  1.26
B) 5 : 4  1.25
3
C) 21 / 12  21 / 4  1.19
D) 6 : 5  1.2
E) 3:2=1.5
37. How many octaves have 12 perfect fifth?
A)
B)
C)
D)
E)
5
6
7
8
9
38. In Pythagorean scale what is the ratio of F and C frequencies ( f F f C )?
A)
B)
C)
D)
E)
4/3
3/2
9/8
256/243
None of the above
39. Just intonation is based on major triads with frequency ratios:
A)
B)
C)
D)
E)
1:2:3
4:5:6
7:8:9
1:3/2:2
1:5/4:2
40. Which scale has a circle of fifths that closes exactly?
A)
B)
C)
D)
E)
The equal temperament scale
The Pythagorean scale
The just intonation scale
The mean tone intonation scale
None of the above
Page 5 of 8
Physics 198
Exam 2
One Dimensional motion
Average Velocity:
v  x / t
Instantaneous Velocity: v  lim x / t
t 0
Average acceleration: a  v / t
Instantaneous acceleration: a  lim v / t
t  0
For constant acceleration only
a  v / t
x  x0  v0 x t  12 a x t 2
v x  v0 x  a x t
y  y 0  v 0 y t  12 gt 2
v x  v0 x
v y  v 0 y  gt
g  9.80 m / s 2
(String)
v  331.3  0.6t m / s (For air)
r2  r1  n  constructive
r2  r1  n  12   destructive
Strings & tubes (fixed /closed at one end)
n  1,3,5...
Newton’s Laws, Forces


F  ma


FAB   FBA
F  kx
Waves

v   f
T
F
m
; 
v
L

Strings & tubes (symmetric)
n  1,2,3...

2L
n n  L  n 
2
n
v
nv
fn 

 nf1
n 2 L
Projectile motion
x  x0  v0 x t
F  mg
Fall 2014
n
n
4
fn 
(Gravity)
(Spring)
 L  n 
v
n

4L
n
nv
 nf 1
4L
Reflection 1   2
sin  2 v2 2


Refraction
sin 1 v1 1
Work, Energy
W  Fd cos
K  12 mv 2
U  mgh
(Gravity)
2
1
U  2 kx
(Spring)
Doppler Effect
 v  vL
f L  f S 
 v  vS



Oscillations
2
  2f 
T
x  A cos(t   )
v   A sin( t   )
a   A 2 cos(t   )
f 
1
2
k
1
; f 
m
2
g
v a
; f 
l
2 Vl
Page 6 of 8
Physics 198
Exam 2
Logarithms
10b  c  b  log 10 c  log c
log AB  log A  log B
log  A / B   log A  log B
Fall 2014
Equal temperament
Semitone ratio: 21 12  1.05946
Whole tone ratio:
2 
1 / 12 2
 21 6  1.12246  1.05946
2
log An  n log A
log 1  0
log 2  0.301
log 10  1
P
A
Area of sphere: A  4r 2
Intensity: I 
Decibels
LP  10dB log
P
; P0  10 12 W
P0
I
LI  10dB log ; I 0  10 12 W / m 2
I0
p
L pr  20dB log
; p0  2 10 5 N / m 2
p0
I  nI1  LI 1  10dB log n
I  2 I1  LI 1  10dB log 2  LI 1  3dB
I
 10 LI 10dB
I0
Beats: fbeats  f 2  f1
Consonant intervals
f2:f1 Interval’s name Examples #of half
steps
1:1 unison
(C, C)
0
2:1 octave
(C, C)
12
3:2 perfect fifth
(C, G)
7
4:3 perfect fourth
(C, F)
5
5:3 major six
(C, A)
9
5:4 major third
(C, E)
4
8:5 minor six
(C, Ab)
8
6:5 minor third
(C, Eb)
3
Page 7 of 8
Physics 198
Exam 2
Fall 2014
Record Sheet
You may fill in this sheet with your choices, detach it and take it with you after the exam for
comparison with the posted answers
1
11
2
12
3
13
4
14
5
15
6
16
7
17
8
18
9
19
10
20
Page 8 of 8