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Wave Motion
1. When a sound wave of frequency 300 Hz passes through a medium the
maximum displacement of a particle of the medium is 0.1 cm. The maximum
(a) 60 π cm/sec
(b) 30 π cm/sec
(c) 30 cm/sec
(d) 60 cm/sec
co
m
velocity of the particle is equal to
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2. In a sinusoidal wave, the time required for a particular point to move from
maximum displacement to zero displacement is 0.170 second. The frequency of
the wave is
(a) 1.47 Hz
(b) 0.36 Hz
(c) 0.73 Hz
(d) 2.94 Hz
3. A stone is dropped into a lake from a tower 500 meter high. The sound of the
splash will be heard by the man approximately after
(b) 21 seconds
(c) 10 seconds
(d) 14 seconds
ks
hi
(a) 11.5 seconds
4. When sound waves travel from air to water, which of the following remains
.s
a
constant
(b) Frequency
(c) Wavelength
(d) All the above
w
(a) Velocity
w
w
5. The speed of a wave in a medium is 760 m/s. If 3600 waves are passing through a
point, in the medium in 2 minutes, then its wavelength is
(a) 13.8 m
(b) 25.3 m
(c) 41.5 m
(d) 57.2 m
6. The temperature at which the speed of sound in air becomes double of its value
at
0o C
is
(a) 273K
(b) 546K
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(c) 1092K
(d) 0K
7. If wavelength of a wave is
λ = 6000 Å.
Then wave number will be
(a)
166 × 10 3
m–1
(b) 16 .6 × 10 −1 m–1
(c)
1 . 66 × 10 6
m–1
(d) 1 .66 × 10 7 m–1
co
m
8. Velocity of sound measured in hydrogen and oxygen gas at a given temperature
will be in the ratio
(b) 4 : 1
(c) 2 : 1
(d) 1 : 1
ed
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(a) 1 : 4
9. Find the frequency of minimum distance between compression & rarefaction of
a wire. If the length of the wire is 1m & velocity of sound in air is 360 m/s
(a) 90 sec–1
(b) 180s–1
(c) 120 sec–1
(d) 360 sec–1
10. The velocity of sound is vs in air. If the density of air is increased to 4 times, then
the new velocity of sound will be
vs
2
(b)
(c)
12 v s
(d)
vs
12
hi
(a)
ks
3 2
vs
2
.s
a
11. It takes 2.0 seconds for a sound wave to travel between two fixed points when the
day temperature is
10 o C.
If the temperature rise to
30 o
C the sound wave travels
w
between the same fixed parts in
w
w
(a) 1.9 sec
(c) 2.1 sec
(b) 2.0 sec
(d) 2.2 sec
12. If vm is the velocity of sound in moist air, vd is the velocity of sound in dry air,
under identical conditions of pressure and temperature
(a) vm > vd
(b) vm < vd
(c) vm = vd
(d) vmvd = 1
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13. A man, standing between two cliffs, claps his hands and starts hearing a series of
echoes at intervals of one second. If the speed of sound in air is 340 ms-1, the
(a) 340 m
(b) 1620 m
(c) 680 m
(d) 1700 m
co
m
distance between the cliffs is
14. A source of sound of frequency 600 Hz is placed inside water. The speed of sound
in water is 1500 m/s and in air is 300 m/s. The frequency of sound recorded by an
ed
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observer who is standing in air is
(a) 200 Hz
(b) 3000 Hz
(c) 120 Hz
(d) 600 Hz
15. If the temperature of the atmosphere is increased the following character of the
sound wave is effected
(a) Amplitude
(b) Frequency
(c) Velocity
(d) Wavelength
16. An underwater sonar source operating at a frequency of 60 KHz directs its beam
hi
towards the surface. If the velocity of sound in air is 330 m/s, the wavelength and
ks
frequency of waves in air are:
.s
a
(a) 5.5 mm, 60 KHz (b) 330 m, 60 KHz
(c) 5.5 mm, 20 KHz (d) 5.5 mm, 80 KHz
w
17. Two sound waves having a phase difference of 60° have path difference of
w
w
(a) 2λ
(c) λ/6
(b) λ/2
(d) λ/3
18. Water waves are
(a) Longitudinal
(b) Transverse
(c) Both longitudinal and transverse
(d) Neither longitudinal nor transverse
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19. Transverse waves can propagate in
(a) Liquids
(b) Solids
(c) Gases
(d) None of these
(a) Transverse
(b) Longitudinal
(c) De-Broglie waves
(d) All the above
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21. Which of the following is not the transverse wave
co
m
20. Sound waves in air are
(a) X-rays
(b) γ -rays
(c) Visible light wave
(d)Sound wave in a gas
22. What is the phase difference between two successive crests in the wave
(a) π
(b) π/2
(c) 2π
(d) 4π
23. A wave of frequency 500 Hz has velocity 360 m/sec. The distance between two
(c) 60 cm
(b) 12 cm
ks
(a) 0.6 cm
hi
nearest points 60° out of phase, is
(d) 120 cm
.s
a
24. The following phenomenon cannot be observed for sound waves
(b) Interference
(c) Diffraction
(d) Polarisation
w
(a) Refraction
w
w
25. When an aero plane attains a speed higher than the velocity of sound in air, a
loud bang is heard. This is because
(a) It explodes
(b) It produces a shock wave which is received as the bang
(c) Its wings vibrate so violently that the bang is heard
(d) The normal engine noises undergo a Doppler shift to generate the bang
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26. The equation of a transverse wave is given by
y = 10 sin π (0 . 01 x − 2 t)
where x and y
are in cm and t is in second. Its frequency is
2 sec −1
(a)
10 sec −1
(b)
(c)
1 sec −1
(d) 0 .01 sec −1
and
y 2 = a cos(ω t − kx )
between the two waves is
(c)
π
(b) π
4
π
(d)
8
π
2
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(a)
The phase difference
co
m
y1 = a sin(ωt − kx )
27. Two waves are given by
28. A wave is reflected from a rigid support. The change in phase on reflection will
be
(a)
(b) π / 2
π /4
(c) π
(d)
2π
29. The equation of a wave travelling in a string can be written as y = 3 cos π (100 t − x ) .
hi
Its wavelength is
(b) 2 cm
ks
(a) 100 cm
(c) 5 cm
(d) None of the above
.s
a
30. A transverse wave is described by the equation Y
x⎞
⎛
= Y0 sin 2π ⎜ ft − ⎟ .
λ
⎝
⎠
The maximum
particle velocity is four times the wave velocity if
πY 0
w
λ=
4
w
w
(a)
(c)
λ = πY0
(b) λ = πY0
2
(d) λ = 2πY0
31. A transverse wave is represented by the equation
y = y 0 sin
2π
λ
(vt − x )
For what value ofλ, the maximum particle velocity equal to two times the wave
velocity
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(a)
λ = 2πy 0
(b) λ = πy 0 / 3
(c)
λ = πy 0 / 2
(d) λ = πy 0
32. A travelling wave in a stretched string is described by the equation y = A sin(kx − ωt) .
The maximum particle velocity is
(b) ω/k
(c) dω/dk
(d) x/t
co
m
(a) Aω
33. A wave travels in a medium according to the equation of displacement given by
.Where y and x are in meters and t in seconds. The
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y(x , t) = 0 .03 sin π (2 t − 0 .01 x )
wavelength of the wave is
(a) 200 m
(b) 100 m
(c) 20 m
(d) 10 m
34. The equation of a sound wave is
wave is
y = 0 .0015 sin(62 .4 x + 316 t)
(b) 0.1 unit
(c) 0.3 unit
(d) Cannot be calculated
hi
(a) 0.2 unit
ks
35. If the equation of transverse wave is
The wavelength of this
x ⎤
⎡ t
y = 5 sin 2π ⎢
−
⎥
⎣ 0 . 04 40 ⎦
, where distance is in cm
.s
a
and time in second, then the wavelength of the wave is
(b) 40 cm
(c) 35 cm
(d) 25 cm
w
(a) 60 cm
w
w
36. A wave is represented by the equation :
y = a sin(0 . 01 x − 2 t)
where a and x are in cm.
velocity of propagation of wave is
(a) 10 cm/s
(b) 50 cm/s
(c) 100 cm/s
(d) 200 cm/s
37. The equation of a longitudinal wave is represented as y = 20 cos π (50 t − x ) . Its
wavelength is
(a) 5 cm
(b) 2 cm
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(c) 50 cm
(d) 20 cm
38. A wave travelling in positive X-direction with
λ = 60 m ,
then correct expression for the wave is
(a)
⎡ ⎛
x ⎞⎤
y = 0 . 2 sin ⎢ 2π ⎜ 6 t +
⎟⎥
60 ⎠⎦
⎣ ⎝
(b) y = 0 .2 sin ⎡⎢π ⎛⎜ 6 t +
x
60
(c)
⎡ ⎛
x ⎞⎤
y = 0 . 2 sin ⎢ 2π ⎜ 6 t −
⎟⎥
60 ⎠ ⎦
⎣ ⎝
(d) y = 0 .2 sin ⎡⎢π ⎛⎜ 6 t −
x ⎞⎤
⎟⎥
60 ⎠⎦
⎣ ⎝
⎣ ⎝
39. The equation of a wave motion (with
t
⎞⎤
⎟⎥
⎠⎦
in seconds and
x
The velocity of the wave will be
in meters) is given by
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π⎤
⎡
y = 7 sin ⎢7πt − 0 . 4 πx + ⎥ .
3⎦
⎣
(a)17.5 m/s
(b)
49 π
49
m/s
2π
(d)
2π
m/s
49
(c)
has a velocity of 360
co
m
m/sec. if
A = 0 .2m
m/s
40. Two waves represented by the following equations are travelling in the same
medium
y1 = 5 sin 2π (75 t − 0.25 x ) , y 2 = 10 sin 2π (150 t − 0 .50 x )
The intensity ratio
I1 / I 2
of the two waves is
(b) 1 : 4
(c) 1 : 8
(d) 1 : 16
ks
hi
(a) 1 : 2
41. The equation of a progressive wave is y = 8 sin ⎡⎢π ⎛⎜
t
−
x⎞ π⎤
⎟+ ⎥.
4 ⎠ 3⎦
The wavelength of the
.s
a
⎣ ⎝ 10
wave is
(b) 4 m
w
(a) 8 m
w
w
(c) 2 m
(d) 10 m
42. Which of the following is not true for this progressive wave
where
y
and
x
are in cm &
t
in sec
(a) Its amplitude is 4 cm
(b) Its wavelength is 100 cm
(c) Its frequency is 50 cycles/sec
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x ⎞
⎛ t
y = 4 sin 2π ⎜
−
⎟
0
.
02
100
⎠
⎝
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(d) Its propagation velocity is
cm/sec
50 × 10 3
43. The equation of a wave is given as y = 0 .07 sin(12πx − 3000 πt) . Where
x
is in meter and
(a)
λ = 1 / 6 m, v = 250 m / s
(b) a = 0.07 m, v = 300 m / s
(c)
n = 1500 , v = 200 m / s
(d) None
44. The equation of the propagating wave is
y = 25 sin( 20 t + 5 x ),
is. Which of the following statement is not true
where
y
displacement
ed
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(a) The amplitude of the wave is 25 units.
co
m
in sec, then the correct statement is
t
(b) The wave is propagating in positive x -direction.
(c) The velocity of the wave is 4 units.
(d) The maximum velocity of the particles is 500 units.
45. In a plane progressive wave given by
frequency are respectively
(a) 25,100
(b) 25, 1
(c) 25, 2
(d)
hi
y
of a wave travelling in the x-direction is given by
meters, where
x
is expressed in metres and
t
in seconds. The
.s
a
π⎞
⎛
y = 10 − 4 sin ⎜ 600 t − 2 x + ⎟
3⎠
⎝
the amplitude and
2
ks
46. The displacement
50 π ,
y = 25 cos( 2πt − πx ) ,
speed of the wave-motion, in ms–1, is
w
(a) 200
w
w
(c) 600
(b) 300
(d) 1200
47. The displacement y of a particle in a medium can be expressed as:
y = 10 −6 sin(100 t + 20 x + π / 4 )m ,
where t is in second and x in meter. The speed of wave
is
(a) 2000 m/s
(b) 5 m/s
(c) 20 m/s
(d) 5π m / s
48. If the wave equation
y = 0 . 08 sin
2π
λ
(200 t − x )
then the velocity of the wave will be
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(a)
(b)
400 2
(c) 400
49. The
200 2
(d) 200
phase
difference
between
two
waves
represented
by
y1 = 10 −6 sin[100 t + ( x / 50 ) + 0 . 5 ]m
co
m
y 2 = 10 −6 cos [100 t + ( x / 50 )]m
Where x is expressed in meters and t is expressed in seconds, is approximately
(b) 1.07 rad
(c) 2.07 rad
(d) 0.5 rad
ed
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(a) 1.5 rad
50. Equation of motion in the same direction are given by
y 2 = 2a sin(ωt − kx − θ )
y1 = 2a sin(ωt − kx )
and
The amplitude of the medium particle will be
(a) 2a cos θ
(b)
2a cos θ
(c) 4 a cos θ / 2
(d)
2 a cos θ / 2
51. A particle on the trough of a wave at any instant will come to the mean position
after a time (T = time period)
(b)
T /2
T /4
hi
(a)
(d)
2T
velocity is
ks
(c) T
(a) 4 units
(b) 2 units
(c) 0
(d) 6 units
Y = 2 sin(kx − 2 t),
then the maximum particle
w
.s
a
52. If the equation of transverse wave is
w
w
53. Equation of motion in the same direction is given by y1 = A sin(ωt − kx ) ,
y 2 = A sin(ωt − kx − θ )
. The amplitude of the medium particle will be
(a)
(c)
2 A cos
θ
(b)
2
2 A cos
θ
2
2 A cos θ
(d) 1.2 f , 1.2λ
54. Two waves having the intensities in the ratio of 9: 1 produce interference. The
ratio of maximum to the minimum intensity, is equal to
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(a) 2 : 1
(b) 4 : 1
(c) 9 : 1
(d) 10 : 8
55. The displacement of the interfering light waves are
y1 = 4 sin ω t
and y 2 = 3 sin⎛⎜ ω t + π ⎞⎟ .
⎝
2⎠
(a) 5
(b) 7
(c) 1
(d) 0
co
m
What is the amplitude of the resultant wave
56. The equation of stationary wave along a stretched string is given by
πx
3
cos 40 πt
, where x and y are in cm and t in second. The separation
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y = 5 sin
between two adjacent nodes is
(a) 1.5 cm
(b) 3 cm
(c) 6 cm
(d) 4 cm
57. A wave represented by the given equation
y = a cos(kx − ω t)
is superposed with
another wave to form a stationary wave such that the point x = 0 is a node. The
equation for the other wave is
(c)
y = −a cos(kx − ω t)
(b) y = −a cos(kx + ω t)
hi
y = a sin(kx + ω t)
(d)
y = −a sin(kx − ω t)
ks
(a)
.s
a
58. A standing wave having 3 nodes and 2 antinodes is formed between two atoms
having a distance 1.21 Å between them. The wavelength of the standing wave is
w
(a) 1.21 Å
w
w
(c) 6.05 Å
(b) 2.42 Å
(d) 3.63 Å
59. A standing wave is represented by Y
= A sin(100 t) cos( 0 . 01 x )
where Y and A are in
millimeter, t is in seconds and x is in meter. The velocity of wave is
(a)
10 4 m / s
(b) 1 m / s
(c)
10 −4 m / s
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(d) Not derivable from above data
60. Equation of a stationary wave is
y = 10 sin
πx
4
cos 20 πt.
Distance between two
(a) 4
(b) 2
(c) 1
(d) 8
co
m
consecutive nodes is
61. At nodes in stationary waves
(a) Change in pressure and density are maximum
(c) Strain is zero
(d) Energy is minimum
62. Consider the three waves
ed
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(b) Change in pressure and density are minimum
z1 , z 2
and
z3
as
z1 = A sin(kx − ω t) , z 2 = A sin(kx + ω t)
and z 3 = A sin(ky − ω t) . Which of the following represents a standing wave?
(a)
z1 + z 2
(b)
z2 + z3
(c)
z 3 + z1
(d)
z1 + z 2 + z 3
hi
63. The following equations represent progressive transverse waves Z1 = A cos(ω t − kx ) ,
ks
Z 2 = A cos(ω t + kx ) , Z3 = A cos(ω t + ky )
and
Z4 = A cos(2ω t − 2ky ) .
A stationary wave will be
.s
a
formed by superposing
Z1
and
Z2
(b)
Z1
and
Z4
(c)
Z2
and
Z3
(d)
Z3
and
Z4
w
(a)
w
w
64. Two travelling waves
y1 = A sin[k (x − c t)]
and
y 2 = A sin[k (x + c t)]
are superimposed on
string. The distance between adjacent nodes is
(a)
c t /π
(b) c t / 2π
(c)
π / 2k
(d) π / k
65. A string vibrates according to the equation y = 5 sin ⎛⎜ 2πx ⎞⎟ cos 20 πt , where x and y are
⎝ 3 ⎠
in cm and t in sec. The distance between two adjacent nodes is
(a) 3 cm
(b) 4.5 cm
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(c) 6 cm
(d) 1.5 cm
1
2
a
3
a
a
4
5
b
b
c
16 a
7
c
17 c
8
b
a
10 a
19 b
20 b
11 a
12 a
13 a
14 d
21 d
22 c
23 b
24 d
25 b
26 c
27 d
28 c
29 b
30 b
31 d
32 a
33 a
34 b
35 b
36 d
37 b
38 c
39 a
40 b
41 a
42 d
43 a
44 b
45 b
46 b
47 b
48 d
49 b
50 c
51 b
52 a
53 a
54 b
55 a
56 b
57 b
58 a
59 a
60 a
61 a
62 a
63 a
64 d
65 d
ks
hi
2. (a)
T
1
=
4 4n
t=
⇒
n=
1
1
=
= 1 . 47 Hz
4 t 4 × 0 . 170
⎛ 2h ⎞
⎛ 2 × 500 ⎞
⎜⎜ ⎟⎟ = ⎜
⎟ = 10 sec
⎝ 10 ⎠
⎝ g⎠
and
w
w
w
3. (a) t1 =
Total time
5.
n=
3600
Hz
2 × 60
6.
v∝ T
7.
n =
1
λ
Hints
= aω = a × 2πn = 0 . 1 × 2π × 300 = 60π cm / sec
.s
a
1. (a) vmax
⇒
=
t2 =
h 500
=
≈ 1 . 5 sec
v 340
= t1 + t 2 = 10 + 1.5 = 11 .5 sec .
⇒
λ=
18 c
9
ed
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n.
15 c
6
co
m
Key
v 760
=
= 25 . 3
n
30
m.
2
⎛v ⎞
T2
v
= 2 ⇒ T2 = T1 ⎜⎜ 2 ⎟⎟ ⇒ T2 = 273 × 4 = 1092 K
T1
v1
⎝ v1 ⎠
1
= 1 . 66 × 10 6 m −1
6000 × 10 −10
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8.
1
v∝
⇒
M
1
∝
10. v sound
ρ
vH2
=
v O2
⇒
M O2
vH
32
4
⇒ 2 =
2
v O2
1
=
M H2
ρ2
=
ρ1
v1
=
v2
4
v
v
= 2 ⇒ v2 = 1 = s
1
2
2
11. t = d and v ∝ T ⇒ t1 = v2 = T2
2
=
t2
⇒ (d1 + d 2 ) =
1.9 sec.
v × t 340 × 2
=
2
2
2π
= 0 . 01π
⇒ λ = 200 m.
33.
k=
35.
⎡t x⎤
y = a sin 2π ⎢ − ⎥
⎣T λ ⎦
ω
v=
=
k
ω
λ = 40 cm
2
= 200 cm / sec
0.01
.
7π
= 17 . 5 m / s
0 .4π
v=
40.
I1 a12
I
25
1
=
⇒ 1 =
=
I2 a22
I2 100 4
43.
ω = 3000 π
.s
a
ks
39.
k
=
⇒
hi
λ
=340 m.
λ
λ π λ v
360
×ϕ =
× = =
=
= 0.12 m = 12 cm
2π
2π 3 6 6n
6 × 500
23. Path difference =
36.
T1
2 d1 2 d 2
2
⇒ t = (d1 + d 2 )
+
v
v
v
t=
13.
303
⇒ t2 =
283
v1
ed
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n.
⇒
t2
n=
ω
2π
= 1500 Hz
w
⇒
k=
w
w
and
,
2π
λ
= 12π ⇒ λ =
v = n λ ⇒ v = 1500 ×
46. v = ω
k
=
co
m
v
1
m
6
1
= 250 m / s
6
600
= 300 m / sec .
2
49. y1 = 10 −6 sin [100 t + (x / 50 ) + 0 .5 ]
⎡
⎛ x ⎞ ⎛ π ⎞⎤
y 2 = 10 − 6 sin ⎢100 t + ⎜ ⎟ + ⎜ ⎟⎥
⎝ 50 ⎠ ⎝ 2 ⎠⎦
⎣
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= [100 t + ( x / 50 ) + 1 . 57 ] − [100 t + ( x / 50 ) + 0 . 5 ]
= 1 . 07
radians.
2
⎞
⎛ I1
⎜
+ 1⎟
⎟
⎜ I
2
⎠ =
=⎝
2
⎛ I1
⎞
⎜
− 1⎟
⎟
⎜ I
⎝ 2
⎠
2
⎞
⎛ 9
⎜
+ 1⎟
⎟
⎜ 1
⎠ = 4
⎝
2
1
⎞
⎛ 9
⎜
− 1⎟
⎟
⎜ 1
⎠
⎝
54.
Imax
Imin
55.
φ=
65.
⎛ 2πx ⎞
y = 5 sin ⎜
⎟ cos 20 π t,
⎝ 3 ⎠
π
⇒
A = a12 + a22 = (4 )2 + (3)2 = 5
ed
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2
co
m
φ
y = 2 a sin
2πx
λ
cos
2πvt
λ
⇒ λ = 3,
w
w
w
.s
a
ks
hi
Require distance = λ / 2 = 1 . 5 cm .
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Beats
1.
A tuning fork arrangement (pair) produces 4 beats/ sec with one fork of
frequency 288 cps. A little wax is placed on the unknown fork and it then
3.
(b) 292 cps
(c) 294 cps
(d) 288 cps
A tuning fork vibrates with 2 beats in 0.04 second. The frequency of the fork is
(a) 50 Hz
(b) 100 Hz
(c) 80 Hz
(d) None of these
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2.
(a) 286 cps
co
m
produces 2 beats/ sec. The frequency of the unknown fork is
Two sound sources when sounded simultaneously produce four beats in 0.25
second. the difference in their frequencies must be
4.
(a) 4
(b) 8
(c) 16
(d) 1
A tuning fork of known frequency 256 Hz makes 5 beats per second with the
hi
vibrating string of a piano. The beat frequency decreases to 2 beats per second
when the tension in the piano string is slightly increased. The frequency of the
(c) 256 – 2 Hz
(d) 256 – 5Hz
When temperature increases, the frequency of a tuning fork
w
5.
(b) 256 + 2Hz
.s
a
(a) 256 + 5 Hz
ks
piano string before increasing the tension was
w
w
(a) Increases
(b) Decreases
(c) Remains same
(d) Increases or decreases depending on the material
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6.
Two strings X and Y of a sitar produce a beat frequency 4 Hz. When the
tension of the string Y is slightly increased the beat frequency is found to be 2
Hz. If the frequency of X is 300 Hz, then the original frequency of Y was
(b) 298 Hz
(c) 302 Hz
(d) 304 Hz
co
m
7.
(a) 296 Hz
The frequency of tuning forks A and B are respectively 3% more and 2% less
than the frequency of tuning fork C. When A and B are simultaneously excited,
5 beats per second are produced. Then the frequency of the tuning fork 'A' (in
(b) 100
(c) 103
(d) 105
When a tuning fork vibrates, the waves produced in the fork are
(a) Longitudinal
(b) Transverse
(c) Progressive
(d) Stationary
Two vibrating tuning forks produce progressive waves given by
Y 2 = 2 sin 506 πt.
Y1 = 4 sin 500 πt and
hi
9.
(a) 98
Number of beats produced per minute is
(a) 360
(d) 60
.s
a
(c) 3
(b) 180
ks
8.
ed
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n.
Hz) is
10. When a tuning fork produces sound waves in air, which one of the following is
w
same in the material of tuning fork as well as in air
w
w
(a) Wavelength
(c) Velocity
(b) Frequency
(d) Amplitude
11. The disc of a siren containing 60 holes rotates at a constant speed of 360 rpm.
The emitted sound is in unison with a tuning fork of frequency
(a) 10 Hz
(b) 360 Hz
(c) 216 Hz
(d) 6 Hz
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12. A sound source of frequency 170 Hz is placed near a wall. A man walking from
a source towards the wall finds that there is a periodic rise and fall of sound
intensity. If the speed of sound in air is 340 m/s the distance (in metres)
(a) 1/2
(b) 1
(c) 3/2
(d) 23
co
m
separating the two adjacent positions of minimum intensity is
1
b
a
3
4
c
12 b
d
5
6
b
a
7
c
hi
11 b
2
ed
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n.
Key
ks
Hints
nA = n +
3n 103 n
=
100
100
w
7.
4
= 16
0 . 25
.s
a
3. Number of beats =
w
w
n A − nB = 5 ⇒
∴
12.
nA =
and
nB = n −
2n
98
=
100 100
5n
= 5 ⇒ n = 100 Hz
100
(103 )(100 )
= 103 Hz
100
v = nλ
Required distance =
λ
2
=
⇒
λ=
v
340
=
n 170
⇒
λ =2
2
=1m
2
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8
a
9
b
10 b
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Vibration of String
1.
A tuning fork vibrating with a sonometer having 20 cm wire produces 5 beats
per second. The beat frequency does not change if the length of the wire is
(b) 210
(c) 205
(d) 215
A stretched string of length
wavelength
3.
λ,
given by
l,
fixed at both ends can sustain stationary waves of
ed
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2.
(a)200
co
m
changed to 21 cm. the frequency of the tuning fork (in Hertz) must be
(a)
λ=
n2
2l
(b)
(c)
λ=
2l
n
(d) λ = 2l n
λ=
l2
2n
A second harmonic has to be generated in a string of length l stretched between
are
hi
two rigid supports. The point where the string has to be plucked and touched
l
4
and touch at
l
2
(b) Plucked at
l
4
and touch at
3l
4
(c) Plucked at
l
2
and touched at
l
4
l
2
and touched at
3l
4
w
.s
a
ks
(a) Plucked at
w
w
(d) Plucked at
4.
Transverse waves of same frequency are generated in two steel wires A and B.
The diameter of A is twice of B and the tension in A is half that in B. The ratio
of velocities of wave in A and B is
(a)
1:3 2
(b) 1 : 2
(c)
1:2
(d)
2
2 :1
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5.
A sonometer wire resonates with a given tuning fork forming standing waves
with five antinodes between the two bridges when a mass of 9 kg is suspended
from the wire. When this mass is replaced by a mass M, the wire resonates with
the same tuning fork forming three antinodes for the same positions of the
6.
(a) 25 kg
(b) 5 kg
(c) 12.5 kg
(d) 1/25 kg
co
m
bridges. The value of M is
The tension of a stretched string is increased by 69%. In order to keep its
7.
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frequency of vibration constant, its length must be increased by
(a) 20%
(b) 30%
(c)
(d) 69%
69 %
A string in musical instrument is 50 cm long and its fundamental frequency is
800 Hz. If a frequency of 1000 Hz is to be produced, then required length of
string is
(c) 40 cm
(d) 37.5 cm
hi
(b) 50 cm
Two wires are in unison. If the tension in one of the wires is increased by 2%, 5
ks
8.
(a) 62.5 cm
.s
a
beats are produced per second. The initial frequency of each wire is
(c) 500 Hz
(d) 1000 Hz
w
(b) 400 Hz
Two uniform strings A and B made of steel are made to vibrate under the same
tension. if the first overtone of A is equal to the second overtone of B and if the
w
w
9.
(a) 200 Hz
radius of A is twice that of B, the ratio of the lengths of the strings is
(a) 1: 2
(b) 1 : 3
(c) 1 : 4
(d) 1 : 6
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10. If the length of a stretched string is shortened by 40% and the tension is
increased by 44%, then the ratio of the final and initial fundamental
(a) 2 : 1
(b) 3 : 2
(c) 3 : 4
(d) 1 : 3
co
m
frequencies is
11. Two wires are fixed in a sonometer. Their tensions are in the ratio 8: 1. The
lengths are in the ratio
36 : 35 .
The diameters are in the ratio 4: 1. Densities of
the materials are in the ratio 1: 2. If the lower frequency in the setting is 360
(a)5
(b) 8
(c) 6
(d) 10
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Hz. the beat frequency when the two wires are sounded together is
12. The first overtone of a stretched wire of given length is 320 Hz. The first
harmonic is
(b) 160 Hz
(c) 480 Hz
(d) 640 Hz
hi
(a) 320 Hz
ks
13. Two perfectly identical wires are in unison. When the tension in one wire is
.s
a
increased by 1%, then on sounding them together 3 beats are heard in 2 sec.
The initial frequency of each wire is
220 s −1
150 s −1
w
(a)
(c)
(b)
320 s −1
(d)
300 s −1
w
w
14. A tuning fork of frequency 392 Hz resonates with 50 cm length of a string
under tension (T). If length of the string is decreased by 2%, keeping the
tension constant, the number of beats heard when the string and the tuning
fork made to vibrate simultaneously is
(a) 4
(b) 6
(c) 8
(d) 12
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15. The sound carried by air from a sitar to a listener is a wave of the following
type
(a) Longitudinal Stationary
(b) Transverse Progressive
(c) Transverse Stationary
(d) Longitudinal Progressive
co
m
16. In Melde’s experiment in the transverse mode, the frequency of the tuning fork
and the frequency of the waves in the strings are in the ratio
(b) 1 : 2
(c) 2 : 1
(d) 4 : 1
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(a) 1 : 1
17. The frequency of transverse vibrations in a stretched string is 200 Hz. If the
tension is increased four times and the length is reduced to one-fourth the
original value, the frequency of vibration will be
(a) 25 Hz
(b) 200 Hz
(c) 400 Hz
(d) 1600 Hz
18. The fundamental frequency of a sonometer wire is n. If its radius is doubled
and its tension becomes half, the material of the wire remains same, the new
hi
fundamental frequency will be
n
2
(d)
.s
a
(c)
(b)
n
ks
(a) n
2
n
2 2
w
19. In an experiment with sonometer a tuning fork of frequency 256 Hz resonates
with a length of 25 cm and another tuning fork resonates with a length of 16
w
w
cm. Tension of the string remaining constant the frequency of the second
tuning fork is
(a) 163.84 Hz
(b) 400 Hz
(c) 320 Hz
(d) 204.8 Hz
Key
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2
c
11 d
3
c
12 b
4
a
13 d
5
b
14 c
6
a
15 d
b
16 a
7
c
17 d
Hints
4.
n1 l1 = n 2 l2
⇒
( N + 5 ) × 20 = ( N − 5 ) × 21
T
T
=
m
πr 2 ρ
v=
vA rB TA
1
=
=
vB rA TB 2 2
5.
n1 =
5
2l
9g
m
∵
n1 = n2 ⇒
n2 =
and
5
2l
3
2l
⇒
Mg
m
9g
3
=
m
2l
Mg
m
⇒
M = 25
n1l1 = n2l2 ⇒ 800 × 50 = 1000 × l2 ⇒ l2 = 40 cm
8.
Δ n ΔT
=
n
2T
kg.
.s
a
n = 500 Hz .
ks
hi
7.
⎡ 1
2⎢
⎢⎣ 2 l A rA
⎡ 1
T ⎤
⎥=3⎢
πρ ⎥⎦
⎢⎣ 2 lB rB
T ⎤
⎥
πρ ⎥⎦
w
9.
N = 205 Hz .
w
w
lA
l
r
2 rB
2
1
=
⇒ A = × B =
lB
3 rA
lB
3 (2rB ) 3
10. n =
n' 2
=
n 1
.
11. n1
=
n2
1 T
T
⇒n∝
2l m
l
l2
l1
c
18 d
9
2
T1 ⎛ d 2 ⎞ ⎛ ρ 2 ⎞
36
⎟ ⇒ n2 =
×⎜ ⎟ ×⎜
× 360 = 370
T2 ⎜⎝ d1 ⎟⎠ ⎜⎝ ρ1 ⎟⎠
35
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b
10 a
19 b
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n.
1.
8
co
m
1
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Beat frequency =
14. n ∝ 1 ⇒
l
⇒
2
2
× n1 =
× 392 = 7 . 8 ≈ 8 .
100
100
1 T
2l m
⇒ n1
n2
=
l2
l1
T1
1
=
T2
4
n2 = 8 n1 = 8 × 200 = 1600 Hz
n=
18.
⇒
19.
n 2 r1
=
n1 r2
n=
1 1
=
4 8
p
2l
T
m
T2
1
1
= ×
T1
2
2
⇒
=
T
1
2l πr 2 ρ
1
⇒
ed
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io
n.
17. n =
Δn
Δl
=−
n
l
co
m
n 2 − n1 =
n2 − n1 = 10
n∝
T
r
2 2
n2
l
25
= 1 ⇒ n2 =
× 256 = 400 Hz
n1
l2
16
A cylindrical tube, open at both ends, has a fundamental frequency
ks
1.
hi
Organ Pipes
f0
in air.
.s
a
The tube is dipped vertically into water such that half of its length is inside
(a) 3 f0 / 4
(b)
f0
w
water. The fundamental frequency of the air column now is
(d)
2 f0
f0 / 2
w
w
(c)
2.
If the length of a closed organ pipe is 1.5 m and velocity of sound is 330 m/s,
then the frequency for the second note is
3.
(a) 220 Hz
(b) 165 Hz
(c) 110 Hz
(d) 55 Hz
A pipe 30 cm long is open at both ends. Which harmonic mode of the pipe is
resonantly excited by a 1.1 kHz source? (Take speed of sound in air = 330 ms–1)
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4.
(a) First
(b) Second
(c) Third
(d) Fourth
Two closed organ pipes, when sounded simultaneously gave 4 beats per sec. If
5.
(a)185.5 cm
(b) 94.9 cm
(c) 90 cm
(d) 80 cm
A source of sound placed at the open end of a resonance column sends an
pressure is
ρA,
(ρ A + ρ 0 )
(ρ A − ρ 0 )
(c)
ρA
ρA
inside the tube. If the atmospheric
then the ratio of maximum and minimum pressure at the closed
end of the tube will be
(a)
ρ0
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n.
acoustic wave of pressure amplitude
(b)
(ρ A + 2 ρ 0 )
(ρ A − 2 ρ0 )
(d)
1
⎞
⎛
⎜ ρ A + ρ0 ⎟
2
⎠
⎝
1
⎛
⎞
⎜ ρ A − ρ0 ⎟
2
⎝
⎠
Two closed pipe produce 10 beats per second when emitting their fundamental
hi
6.
co
m
longer pipe has a length of 1m. Then length of shorter pipe will be, (v = 300 m/s)
in Hz, are
(c) 260, 250
(d) 260, 280
A closed organ pipe and an open organ pipe are tuned to the same fundamental
w
7.
(b) 260, 270
.s
a
(a) 270, 280
ks
nodes. If their length are in ratio of 25: 26. Then their fundamental frequency
w
w
frequency. What is the ratio of lengths
8.
(a)1 : 2
(b) 2 : 1
(c) 2 : 3
(d) 4 : 3
An open pipe resonates with a tuning fork of frequency 500 Hz. it is observed
that two successive nodes are formed at distances 16 and 46 cm from the open
end. The speed of sound in air in the pipe is
(a) 230 m/s
(b) 300 m/s
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(c) 320 m/s
9.
(d) 360 m/s
Find the fundamental frequency of a closed pipe, if the length of the air column
is 42 m. (speed of sound in air = 332 m/sec)
(b) 4 Hz
(c) 7 Hz
(d) 9 Hz
co
m
(a) 2 Hz
10. If v is the speed of sound in air then the shortest length of the closed pipe which
(a)
v
4n
(b)
v
2n
(c)
2n
v
(d)
4n
v
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n.
resonates to a frequency n
11. The frequency of fundamental tone in an open organ pipe of length 0.48 m is
320 Hz. Speed of sound is 320 m/sec. Frequency of fundamental tone in closed
organ pipe will be
(a) 153.8 Hz
(b) 160.0 Hz
(c) 320.0 Hz
(d) 143.2 Hz
is
(b) 50 Hz
.s
a
(a)100 Hz
ks
hi
12. If fundamental frequency of closed pipe is 50 Hz then frequency of 2nd overtone
(c) 250 Hz
(d) 150 Hz
w
13. Two open organ pipes of length 25 cm and 25.5 cm produce 10 beat/ sec. The
velocity of sound will be
(b) 250 m/s
(c) 350 m/s
(d) None of these
w
w
(a) 255 m/s
14. What is minimum length of a tube, open at both ends, that resonates with
tuning fork of frequency 350 Hz? [velocity of sound in air = 350 m/s]
(a) 50 cm
(b) 100 cm
(c) 75 cm
(d) 25 cm
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15. Two open organ pipes give 4 beats/ sec when sounded together in their
fundamental nodes. If the length of the pipe are 100 cm and 102.5 cm
respectively, then the velocity of sound is
(b) 328 m/s
(c) 240 m/s
(d) 160 m/s
co
m
(a) 496 m/s
16. The harmonics which are present in a pipe open at one end are
(a) Odd harmonics
ed
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n.
(b) Even harmonics
(c) Even as well as odd harmonics
(c) None of these
17. An open pipe is suddenly closed at one end with the result that the frequency of
third harmonic of the closed pipe is found to be higher by 100 Hz, then the
fundamental frequency of open pipe is:
(b) 300 Hz
(c) 240 Hz
(d) 200 Hz
hi
(a) 480 Hz
18. Tube A has both ends open while tube B has one end closed, otherwise they are
(b) 1 : 4
.s
a
(a) 1 : 2
ks
identical. The ratio of fundamental frequency of tube A and B is
(c) 2 : 1
(d) 4 : 1
w
19. If the temperature increases, then what happens to the frequency of the sound
w
w
produced by the organ pipe
(a) Increases
(b) Decreases
(c) Unchanged
(d) Not definite
20. Apparatus used to find out the velocity of sound in gas is
(a) Melde’s apparatus
(b) Kundt’s tube
(c) Quincke’s tube
(d) None of these
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21. In one meter long open pipe what is the harmonic of resonance obtained with a
tuning fork of frequency 480 Hz
(a) First
(b) Second
(c) Third
(d) Fourth
co
m
22. An organ pipe open at one end is vibrating in first overtone and is in resonance
with another pipe open at both ends and vibrating in third harmonic. The ratio
of length of two pipes is
(b) 4 : 1
(c) 8 : 3
(d) 3 : 8
ed
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n.
(a) 1 : 2
23. In a resonance pipe the first and second resonances are obtained at depths 22.7
cm and 70.2 cm respectively. What will be the end correction
(a) 1.05 cm
(b) 115.5 cm
(c) 92.5 cm
(d) 113.5 cm
24. An open tube is in resonance with string (frequency of vibration of tube is n0).
hi
If tube is dipped in water so that 75% of length of tube is inside water, then the
ratio of the frequency of tube to string now will be
2
3
.s
a
(d)
3
2
Key
w
w
w
(c)
(b) 2
ks
(a) 1
1
b
2
b
3
a
4
b
11 b
12 c
13 a
14 a
21 c
22 a
23 a
24 b
5
a
15 b
6
c
16 a
7
a
17 d
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8
b
18 c
9
a
10 a
19 a
20 b
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Hints
3.
n1 =
3v 3 × 330
= 165 Hz
=
4l
4 × 1.5
v
330
=
= 550 Hz
2l 2 × 0 . 3
n = 2 × n1 = 1100
4.
n1 =
.
v
4 l1
and
Hz
n2 =
.=
1.1 kHz
v
4l2
co
m
2. n =
n2 − n1 = 4
Number of beats =
⎝
6.
2
1
⎝
⎠
n1 − n2 = 10
n1 =
v
4l1
⇒
n1 l2
26
=
=
n 2 l1
25
and
n2 =
v
4l2
⎠
hi
n1 = 260 Hz , n2 = 250 Hz
2
ed
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n.
⎛
⎛
⎞
⎞
⇒ 4 = v ⎜ 1 − 1 ⎟ ⇒ 16 = 300 ⎜ 1 − 1 ⎟ ⇒ l2 = 94 . 9 cm
⎜l
1⎟
4 ⎜l
l ⎟
=
λ
2
= 46 − 16 = 30 ⇒ λ = 60
ks
8. Distance between two consecutive nodes
∴ v = n λ = 500 × 0 . 6 = 300 m / s .
v
332
⇒n=
= 2 Hz
4l
4 × 42
n 3 = 5n1 = 5 × 50 = 250 Hz
w
12.
n=
.s
a
9.
w
w
13. (a) Δn = n1 − n2 ⇒ 10 =
⇒ 10 =
14.
n=
15. (b)
v ⎡1 1 ⎤
v
v
= ⎢ − ⎥
−
2 ⎣ l1 l2 ⎦
2 l1 2 l 2
v ⎡ 1
1 ⎤
⇒ v = 255 m / s.
−
2 ⎢⎣ 0 . 25 0 . 255 ⎥⎦
1
350
v
⇒ l = m = 50 cm.
⇒ 350 =
2
2l
2l
Δn = n1 − n2 ⇒ 4 =
V =
v⎡ 1
1 ⎤
v
v
= ⎢
−
−
2 l1 2 l 2
2 ⎣ 1 .00 1 . 025 ⎥⎦
8
≈ 328 m / s.
0.025
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cm = 0.6m
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23.
N =
480
n × 2l
=
× 2 ×1 =
330
v
l2 + x 3 λ / 4
=
=3
l1 + x
λ /4
x=
24.
3
l2 − 3 l1 70 . 2 − 3 × 22 . 7
=
= 1 . 05 cm
2
2
v
2l
n0 =
l' = l ×
n
v
v
v
=2
=
= = 2n0 ⇒
n0
4 l' 4 × (l / 4 ) l
w
w
w
.s
a
ks
hi
ed
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n.
n=
25
l
=
100 4
co
m
21.
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Doppler’s Effect
1.
A sound source is moving towards a stationary observer with 1/10 of the speed
2.
(a) 10/9
(b) 11/10
(c)
(d) (9 / 10 )2
(11 / 10 )2
co
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of sound. The ratio of apparent to real frequency is
A siren emitting sound of frequency 500 Hz is going away from a static listener
ed
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n.
with a speed of 50 m/sec. The frequency of sound to be heard, directly from the
siren is
3.
(a) 434.2 Hz
(b) 589.3 Hz
(c) 481.2 Hz
(d) 286.5 Hz
A source is moving towards an observer with a speed of 20 m/s and having
frequency of 240 Hz. The observer is now moving towards the source with a
speed of 20 m/s. Apparent frequency heard by observer, if velocity of sound is
(b) 270 Hz
(c) 280 Hz
(d) 360 Hz
ks
(a) 240 Hz
A siren placed at a railway platform is emitting sound of frequency 5 kHz. A
.s
a
4.
hi
340 m/s is
passenger sitting in a moving train A records a frequency of 5.5 kHz while the
w
train approaches the siren. During his return journey in a different train B he
w
w
records a frequency of 6.0 kHz while approaching the same siren. The ratio of
the velocity of train B to that of train A is
(a) 242/252
(b) 2
(c) 5/6
(d) 11/6
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5.
A whistle revolves in a circle with an angular speed of 20 rad/sec using a string
of length 50 cm. If the frequency of sound from the whistle is 385 Hz, then what
is the minimum frequency heard by an observer, which is far away from the
6.
(a) 333 Hz
(b) 374 Hz
(c) 385 Hz
(d) 394 Hz
co
m
centre in the same plane ? (v = 340 m/s)
A Siren emitting sound of frequency 800 Hz is going away from a static listener
with a speed of 30 m/s, frequency of the sound to be heard by the listener is
7.
ed
uc
at
io
n.
(take velocity of sound as 330 m/s)
(a) 733.3 Hz
(b) 644.8 Hz
(c) 481.2 Hz
(d) 286.5 Hz
A car sounding a horn of frequency 1000 Hz passes an observer. The ratio of
frequencies of the horn noted by the observer before and after passing of the
car is 11: 9. If the speed of sound is v, the speed of the car is
8.
(b)
1
v
2
1
v
5
(d) v
ks
(c)
1
v
10
hi
(a)
What should be the velocity of a sound source moving towards a stationary
.s
a
observer so that apparent frequency is double the actual frequency (Velocity of
sound is v)?
w
(a) v
v
2
w
w
(c)
9.
(b) 2v
(d)
v
4
Two trains are moving towards each other at speeds of 20 m/s and 15 m/s
relative to the ground. The first train sounds a whistle of frequency 600 Hz. the
frequency of the whistle heard by a passenger in the second train before the
train meets is (the speed of sound in air is 340 m/s)
(a) 600 Hz
(b) 585 Hz
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(c) 645 Hz
(d) 666 Hz
10. A small source of sound moves on a circle as shown in the figure and an
observer is standing on
C
n3 be
the frequencies heard when the
B
C
> n 3 > n1
A
n1 = n 2 > n 3
(d) n 2
and
respectively. Then
n1 > n 2 > n 3
(b) n 2
(c)
and
n1 , n 2
> n1 > n 3
ed
uc
at
io
n.
(a)
A, B
Let
co
m
source is at
O.
11. A source and an observer approach each other with same velocity 50 m/s. If the
apparent frequency is 435 sec–1, then the real frequency is
(a) 320 s–1
(b) 360 sec–1
(c) 390 sec–1
(d) 420 sec–1
12. A source emits a sound of frequency of 400 Hz, but the listener hears it to be
390 Hz. Then
hi
(a) The listener is moving towards the source.
ks
(b) The source is moving towards the listener.
(c) The listener is moving away from the source.
.s
a
(d) The listener has a defective ear.
13. Doppler effect is applicable for
w
(a) Moving bodies
w
w
(b) One is moving and other is stationary
(c) For relative motion
(d) None of these
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14. A source and an observer are moving towards each other with a speed equal to
v
2
where
v
is the speed of sound. The source is emitting sound of frequency n.
The frequency heard by the observer will be
(c)
n
3
(b) n
(d)
3n
co
m
(a) Zero
15. When an engine passes near to a stationary observer then its apparent
frequencies occurs in the ratio 5/3. If the velocity of engine is
(b) 270 m/s
(c) 85 m/s
(d) 52.5 m/s
ed
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at
io
n.
(a) 540 m/s
16. A police car horn emits a sound at a frequency 240 Hz when the car is at rest. If
the speed of the sound is 330 m/s, the frequency heard by an observer who is
approaching the car at a speed of 11 m/s, is :
(a) 248 Hz
(b) 244 Hz
(c) 240 Hz
(d) 230 Hz
hi
17. A person carrying a whistle emitting continuously a note of 272 Hz is running
ks
towards a reflecting surface with a speed of 18 km/hour. The speed of sound in
air is 345 ms −1 . The number of beats heard by him is
(c) 8
(b) 6
.s
a
(a)4
(d) 3
w
18. A bus is moving with a velocity of 5 m/s towards a huge wall. The driver sounds
w
w
a horn of frequency 165 Hz. If the speed of sound in air is 355 m/s, the number
of beats heard per second by a passenger on the bus will be
(a)6
(b) 5
(c) 3
(d) 4
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19. A source of sound of frequency 256 Hz is moving rapidly towards a wall with a
velocity of 5m/s. The speed of sound is 330 m/s. If the observer is between the
(a)7.8 Hz
(b) 7.7 Hz
(c) 3.9 Hz
(d) Zero
co
m
wall and the source, then beats per second heard will be
20. The apparent frequency of a note, when a listener moves towards a stationary
source, with velocity of 40 m/s is 200 Hz. When he moves away from the same
source with the same speed, the apparent frequency of the same note is 160 Hz.
ed
uc
at
io
n.
The velocity of sound in air is (in m/s)
(a) 360
(b) 330
(c) 320
(d) 340
21. An observer moves towards a stationary source of sound, with a velocity onefifth of the velocity of sound. What is the percentage increase in the apparent
frequency
(b) 20%
(c) Zero
(d) 0.5%
1
.s
a
ks
hi
(a) 5%
a
a
12 c
w
11 a
2
3
b
13 c
4
b
14 d
Key
5
b
15 c
6
a
16 a
7
a
17 c
w
w
21 b
1.
⎛ v
n' = n ⎜⎜
⎝ v − vS
⎛
Hints
⎞
v
⎞
⎟ = n ⎛⎜
⎟
⎟
v
v
−
/
10
⎝
⎠
⎠
v
⎝ v + vS
2. ( n′ = n ⎜⎜
⇒
n' 10
=
n
9
⎞
330 ⎞
⎟ = 500 × ⎛⎜
⎟ = 434 .2 Hz
⎟
⎝ 300 + 50 ⎠
⎠
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8
c
18 b
9
d
10 b
19 a
20 a
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⎛
⎞
3. ( n' = n ⎜⎜ v + vO ⎟⎟ = 240 ⎛⎜ 340 + 20 ⎞⎟ = 270 Hz
⎝ v − vS ⎠
⎛ v + vA ⎞
5 .5 = 5 ⎜
⎟
⎝ v ⎠
and
vB
=2
vA
⎛ v
nmin = n ⎜⎜
⎝ v + vs
6.
⎛ 340 ⎞
nmin = 385 ⎜
⎟ = 374 Hz .
⎝ 340 + 10 ⎠
⎛ v
n' = n ⎜⎜
⎝ v + vS
7.
v = rω = 0 .5 × 10 = 1 m / s
where
⎞
330 ⎞
⎟ = 800 ⎛⎜
⎟ = 733 .33 Hz
⎟
+ 30 ⎠
330
⎝
⎠
n Before =
v
n
v − vc
n Before
11 ⎛ v + vc
=⎜
9 ⎜⎝ v − vc
n After =
⎞
⎟
⎟
⎠
⇒
⎛
⎞
9. n′ = n ⎜⎜ v + v0 ⎟⎟ = 600 ⎛⎜ 340 + 15 ⎞⎟ ≈ 666
⎝ v − vs ⎠
15.
w
⎛ v
n' = n ⎜⎜
⎝ v − vS
∴
16.
⎝ 340 − 20 ⎠
⎡ v + vO ⎤
n' = n⎢
⎥
⎣ v − vS ⎦
w
w
11.
v
.n
v + vc
vc ⇒
.s
a
n After
=
and
hi
⇒
⎞
⎟
⎟
⎠
ks
5.
⎛ v + vB ⎞
6 = 5⎜
⎟
⎝ v ⎠
co
m
⎛ v + v0 ⎞
n′ = n ⎜
⎟
⎝ v ⎠
ed
uc
at
io
n.
4.
⎝ 340 − 20 ⎠
⎞
⎟
⎟
⎠
and
v
10
Hz
⎡ 332 + 50 ⎤
−1
1
⇒ 435 = n ⎢
⎥ ⇒ n = 321 . 12 sec ≈ 320 sec
⎣ 332 − 50 ⎦
⎛ v
n ′′ = ⎜⎜
⎝ v + vS
⎞
⎟n
⎟
⎠
n' v + v S
5 340 + v S
⇒ v S = 85 m / s .
⇒ =
=
n' ' v − v S
3 340 − v S
⎛ 330 + 11 ⎞
⎛ v + v0 ⎞
n′ = n ⎜
⎟ = 248 Hz .
⎟ = 240 ⎜
v
⎝ 330 ⎠
⎝
⎠
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17.
n' =
v + v person
v − v person
.272 =
345 + 5
× 272 = 280
345 − 5
Hz
Number of beats =280 – 272 = 8 Hz
n' =
v + vB
355 + 5
×n =
× 165 = 170
v − vB
355 − 5
x
21.
Hz
= n'− n = 170 − 165 = 5
6
⎡ v + vO ⎤
⎡v + v / 5 ⎤
n' = ⎢
⎥n = ⎢ v
⎥ n = 5 n = 1 . 2n
v
⎣
⎦
⎣
⎦
0 . 2n
× 100
n
= 20%.
w
w
w
.s
a
ks
hi
ed
uc
at
io
n.
Percentage change =
co
m
18.
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