Waves- 1 Practice Questions - DPP for NEET

 Page 1


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A tuning fork makes 256 vibrations per second in air. When
the velocity of sound is 330 m/s then wavelength of the tone
emitted is
(a) 0.56 m (b) 0.89 m (c) 1.11 m (d) 1.29 m
Q.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) 1.47Hz (b) 0.36 Hz (c) 0.73 Hz (d) 2.94 Hz
Q.3 A man is standing between two parallel cliffs and fires a
gun. If he hears first and second echoes after 1.5 s and
3.5s respectively, the distance between the cliffs is
(Velocity of sound in air = 340 ms
–1
)
(a) 1190 m
(b) 850 m
(c) 595 m
(d) 510 m
Q.4 v
1 
and v
2 
are the velocities of sound at the same temperature
in two monoatomic gases of densities r
1 
and r
2
respectively. If 
12
1
/
4
r r= then the ratio of velocities v
1
and v
2 
will be
(a) 1 : 2 (b) 4 : 1 (c) 2 : 1 (d) 1 : 4
Q.5 A wave of frequency 500 Hz has velocity 360 m/sec. The
distance between two nearest points 60° out of phase, is
(a) 0.6 cm (b) 12 cm (c) 60 cm (d) 120 cm
Page 2


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A tuning fork makes 256 vibrations per second in air. When
the velocity of sound is 330 m/s then wavelength of the tone
emitted is
(a) 0.56 m (b) 0.89 m (c) 1.11 m (d) 1.29 m
Q.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) 1.47Hz (b) 0.36 Hz (c) 0.73 Hz (d) 2.94 Hz
Q.3 A man is standing between two parallel cliffs and fires a
gun. If he hears first and second echoes after 1.5 s and
3.5s respectively, the distance between the cliffs is
(Velocity of sound in air = 340 ms
–1
)
(a) 1190 m
(b) 850 m
(c) 595 m
(d) 510 m
Q.4 v
1 
and v
2 
are the velocities of sound at the same temperature
in two monoatomic gases of densities r
1 
and r
2
respectively. If 
12
1
/
4
r r= then the ratio of velocities v
1
and v
2 
will be
(a) 1 : 2 (b) 4 : 1 (c) 2 : 1 (d) 1 : 4
Q.5 A wave of frequency 500 Hz has velocity 360 m/sec. The
distance between two nearest points 60° out of phase, is
(a) 0.6 cm (b) 12 cm (c) 60 cm (d) 120 cm
2
DPP/ P 29
Q.6 Two waves are given by 
1
sin() y a t kx = w- and y
2
 = a cos
(wt – kx). The phase difference between the two waves is
(a)
4
p
(b) p (c)
8
p
(d)
2
p
Q.7 The relation between time and displacement for two
particles is given by
22
0.06sin 2 (0.04 ), 0.03sin 2 (1.04 )
1
y tyt = p +f = p +f
The ratio of the intensities of the waves produced by the
vibrations of the two particles will be
(a) 2 : 1 (b) 1 : 2 (c) 4 : 1 (d) 1 : 4
Q.8 A transverse wave is described by the equation
0
sin2.
æö
= p-
ç÷
l èø
x
Y Y ft The maximum particle velocity is four
times the wave velocity if
(a)
0
4
Y p
l= (b)
0
2
Y p
l=
(c)
0
Y l =p (d)
0
2 Y l=p
Q.9 Which one of the following does not represent a travelling
wave?
(a) sin() y x vt =- (b) sin()
m
y y k x vt =+
(c) log()
m
y y x vt =- (d)
22
() y f x vt =-
Q.10The path difference between the two waves
11
2
sin
p æö
= w-
ç÷
l èø
x
yat and 
22
2
cos
p æö
= w - +f
ç÷
l èø
x
yat is
(a)
2
l
f
p
(b)
22
lp æö
f+
ç÷
p
èø
(c)
2
2
pp æö
f-
ç÷
l
èø
(d)
2 p
f
l
Q.11 A transverse wave is represented by the equation
( )
0
2
sin
p
=-
l
y y vtx , Here v = wave velocity
For what value of , l the maximum particle velocity equal
to two times the wave velocity
(a)
0
2 y l=p (b)
0
/3 y l=p
(c)
0
/2 y l =p (d)
0
y l =p
Q.12 The equation of a plane progressive wave is given by
( ) 0.025sin 100 0.25 . y tx =+
 The frequency of this wave
would be
(a)
50
Hz
p
(b)
100
Hz
p
(c)
100Hz
(d)
50Hz
Q.13 A wave travelling in positive X-direction with A = 0.2m
has a velocity of 360 m/sec. If 
l
= 60m, then correct
expression  for the wave is
(a)
0.2sin26
60
x
yt
éù æö
= p+
ç÷ êú
èø ëû
 (b)
0.2sin6
60
x
yt
éù æö
= p+
ç÷ êú
èø ëû
(c)
0.2sin26
60
x
yt
éù æö
= p-
ç÷ êú
èø ëû
 (d)
0.2sin6
60
x
yt
éù æö
= p-
ç÷ êú
èø ëû
Q.14The equation of a wave is given as
( ) 0.07sin12 3000 = p-p y xt . where x is in metre and t in
sec , then the correct statement is
(a) 1/ 6m, 250 m/s v l== (b) 0.07m, 300m/s av ==
(c) 1500, 200 m/s nv == (d) None
Q.15 The  equation of a progressive wave is given by
( ) 0.5sin 20 400 y xt =- where x and y are in metre and
t is in  second. The velocity of the wave is
(a) 10 m/s (b) 20 m/s (c) 200 m/s (d) 400 m/s
Q.16 There is a destructive interference between the two waves
of wavelength 
l
 coming from two different paths at a
point. To get maximum sound or constructive interference
at that point, the path of one wave is to be increased by
(a)
4
l
(b)
2
l
(c)
3
4
l
(d)
l
Q.17If two waves of same frequency and same amplitude on
superimposition produced a resultant disturbance of the
same amplitude, the waves differ in phase by
(a) p (b)
2 p
/3 (c) p / 2 (d) zero
Page 3


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A tuning fork makes 256 vibrations per second in air. When
the velocity of sound is 330 m/s then wavelength of the tone
emitted is
(a) 0.56 m (b) 0.89 m (c) 1.11 m (d) 1.29 m
Q.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) 1.47Hz (b) 0.36 Hz (c) 0.73 Hz (d) 2.94 Hz
Q.3 A man is standing between two parallel cliffs and fires a
gun. If he hears first and second echoes after 1.5 s and
3.5s respectively, the distance between the cliffs is
(Velocity of sound in air = 340 ms
–1
)
(a) 1190 m
(b) 850 m
(c) 595 m
(d) 510 m
Q.4 v
1 
and v
2 
are the velocities of sound at the same temperature
in two monoatomic gases of densities r
1 
and r
2
respectively. If 
12
1
/
4
r r= then the ratio of velocities v
1
and v
2 
will be
(a) 1 : 2 (b) 4 : 1 (c) 2 : 1 (d) 1 : 4
Q.5 A wave of frequency 500 Hz has velocity 360 m/sec. The
distance between two nearest points 60° out of phase, is
(a) 0.6 cm (b) 12 cm (c) 60 cm (d) 120 cm
2
DPP/ P 29
Q.6 Two waves are given by 
1
sin() y a t kx = w- and y
2
 = a cos
(wt – kx). The phase difference between the two waves is
(a)
4
p
(b) p (c)
8
p
(d)
2
p
Q.7 The relation between time and displacement for two
particles is given by
22
0.06sin 2 (0.04 ), 0.03sin 2 (1.04 )
1
y tyt = p +f = p +f
The ratio of the intensities of the waves produced by the
vibrations of the two particles will be
(a) 2 : 1 (b) 1 : 2 (c) 4 : 1 (d) 1 : 4
Q.8 A transverse wave is described by the equation
0
sin2.
æö
= p-
ç÷
l èø
x
Y Y ft The maximum particle velocity is four
times the wave velocity if
(a)
0
4
Y p
l= (b)
0
2
Y p
l=
(c)
0
Y l =p (d)
0
2 Y l=p
Q.9 Which one of the following does not represent a travelling
wave?
(a) sin() y x vt =- (b) sin()
m
y y k x vt =+
(c) log()
m
y y x vt =- (d)
22
() y f x vt =-
Q.10The path difference between the two waves
11
2
sin
p æö
= w-
ç÷
l èø
x
yat and 
22
2
cos
p æö
= w - +f
ç÷
l èø
x
yat is
(a)
2
l
f
p
(b)
22
lp æö
f+
ç÷
p
èø
(c)
2
2
pp æö
f-
ç÷
l
èø
(d)
2 p
f
l
Q.11 A transverse wave is represented by the equation
( )
0
2
sin
p
=-
l
y y vtx , Here v = wave velocity
For what value of , l the maximum particle velocity equal
to two times the wave velocity
(a)
0
2 y l=p (b)
0
/3 y l=p
(c)
0
/2 y l =p (d)
0
y l =p
Q.12 The equation of a plane progressive wave is given by
( ) 0.025sin 100 0.25 . y tx =+
 The frequency of this wave
would be
(a)
50
Hz
p
(b)
100
Hz
p
(c)
100Hz
(d)
50Hz
Q.13 A wave travelling in positive X-direction with A = 0.2m
has a velocity of 360 m/sec. If 
l
= 60m, then correct
expression  for the wave is
(a)
0.2sin26
60
x
yt
éù æö
= p+
ç÷ êú
èø ëû
 (b)
0.2sin6
60
x
yt
éù æö
= p+
ç÷ êú
èø ëû
(c)
0.2sin26
60
x
yt
éù æö
= p-
ç÷ êú
èø ëû
 (d)
0.2sin6
60
x
yt
éù æö
= p-
ç÷ êú
èø ëû
Q.14The equation of a wave is given as
( ) 0.07sin12 3000 = p-p y xt . where x is in metre and t in
sec , then the correct statement is
(a) 1/ 6m, 250 m/s v l== (b) 0.07m, 300m/s av ==
(c) 1500, 200 m/s nv == (d) None
Q.15 The  equation of a progressive wave is given by
( ) 0.5sin 20 400 y xt =- where x and y are in metre and
t is in  second. The velocity of the wave is
(a) 10 m/s (b) 20 m/s (c) 200 m/s (d) 400 m/s
Q.16 There is a destructive interference between the two waves
of wavelength 
l
 coming from two different paths at a
point. To get maximum sound or constructive interference
at that point, the path of one wave is to be increased by
(a)
4
l
(b)
2
l
(c)
3
4
l
(d)
l
Q.17If two waves of same frequency and same amplitude on
superimposition produced a resultant disturbance of the
same amplitude, the waves differ in phase by
(a) p (b)
2 p
/3 (c) p / 2 (d) zero
DPP/ P 29
3
Q.18Equation of motion in the same direction is given by
1
sin( ), y A t kx = w-
2
sin() y A t kx = w - -q .The amplitude
of the medium particle will be
(a) 2 cos
2
A
q
(b)
2 cos A q
(c) 2 cos
2
A
q
(d) 2Acos q
Q.19The amplitude of a wave, represented by displacement
equation 
1
sin cos ytt
ab
1
= w±w will be
(a)
ab
ab
+
(b)
ab
ab
+
(c)
ab
ab
±
(d)
ab
ab
+
Q.20The displacement due to a wave moving in the positive
x -direction is given by 
2
1
(1)
y
x
=
+
at time 
0 t =
and by
2
1
[1 ( 1)]
y
x
=
+-
at 
2 t =
seconds, where x and y are in
metres. The velocity of the wave in m/s is
(a) 0.5 (b) 1 (c) 2 (d)4
DIRECTIONS (Q.21-Q.23) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes : (a) 1, 2 and 3 are correct
(b) 1 and 2 are correct
(c) 2 and 4 are correct
(d) 1 and 3 are correct
Q.21 P , Q and R are three particles of a medium which lie on the
x-axis. A sine wave of wavelength l is travelling through
the medium in the x-direction. P and Q always have the
same speed, while P and R always have the same velocity .
The minimum distance between –
(1) P and Q is l (2) P and Q is l/2
(3) P and R is l/2 (4) P and R is l
Q.22 A wave represented by the given equation
p
Y A sin 10px 15pt
3
æö
= ++
ç÷
èø
, where x is in meter and t is
in second. The expression represents
(1) A wave travelling in the negative X direction with a
velocity of 1.5 m/sec
(2) A wave travelling in the negative X direction with a
wavelength of 0.2 m
(3) A wave travelling in the positive X direction with a
velocity of 1.5 m/sec.
(4) A wave travelling in the positive X direction with a
wavelength of 0.2 m
Q.23 It is usually more convenient to describe a sound wave in
terms of pressure wave as compared to displacement wave
because –
(1) Two waves of same intensity but different frequencies
have different displacement amplitude but same
pressure amplitude
(2) The human ear responds to the change in pressure and
not to the displacement wave.
(3) The electronic detector (microphone) does respond
to the change in pressure but not to the displacement.
(4) None of the above
DIRECTIONS (Q.24-Q.26) : Read the passage given below
and answer the questions that follows :
Sound from a point isotropic source spreads equally in all
directions in homogeneous medium. Therefore its intensity
decreases with square of distance from the source. When
distance between observer and the source changes, apart from
changes in intensity,  the observer listens sound of pitch higher
or lower than actual pitch depending upon the fact that the
distance between the observer and source is decreasing or
increasing respectively. An observer O is at a distance 2R from
centre of a circle of radius R. A point isotropic sound source S
moves on the circle with uniform angular velocity w = p/3 rad/
s.  Initially observer, source and centre of the circle are in same
line.
R=1m
O S C
R
2R
1R
Page 4


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A tuning fork makes 256 vibrations per second in air. When
the velocity of sound is 330 m/s then wavelength of the tone
emitted is
(a) 0.56 m (b) 0.89 m (c) 1.11 m (d) 1.29 m
Q.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) 1.47Hz (b) 0.36 Hz (c) 0.73 Hz (d) 2.94 Hz
Q.3 A man is standing between two parallel cliffs and fires a
gun. If he hears first and second echoes after 1.5 s and
3.5s respectively, the distance between the cliffs is
(Velocity of sound in air = 340 ms
–1
)
(a) 1190 m
(b) 850 m
(c) 595 m
(d) 510 m
Q.4 v
1 
and v
2 
are the velocities of sound at the same temperature
in two monoatomic gases of densities r
1 
and r
2
respectively. If 
12
1
/
4
r r= then the ratio of velocities v
1
and v
2 
will be
(a) 1 : 2 (b) 4 : 1 (c) 2 : 1 (d) 1 : 4
Q.5 A wave of frequency 500 Hz has velocity 360 m/sec. The
distance between two nearest points 60° out of phase, is
(a) 0.6 cm (b) 12 cm (c) 60 cm (d) 120 cm
2
DPP/ P 29
Q.6 Two waves are given by 
1
sin() y a t kx = w- and y
2
 = a cos
(wt – kx). The phase difference between the two waves is
(a)
4
p
(b) p (c)
8
p
(d)
2
p
Q.7 The relation between time and displacement for two
particles is given by
22
0.06sin 2 (0.04 ), 0.03sin 2 (1.04 )
1
y tyt = p +f = p +f
The ratio of the intensities of the waves produced by the
vibrations of the two particles will be
(a) 2 : 1 (b) 1 : 2 (c) 4 : 1 (d) 1 : 4
Q.8 A transverse wave is described by the equation
0
sin2.
æö
= p-
ç÷
l èø
x
Y Y ft The maximum particle velocity is four
times the wave velocity if
(a)
0
4
Y p
l= (b)
0
2
Y p
l=
(c)
0
Y l =p (d)
0
2 Y l=p
Q.9 Which one of the following does not represent a travelling
wave?
(a) sin() y x vt =- (b) sin()
m
y y k x vt =+
(c) log()
m
y y x vt =- (d)
22
() y f x vt =-
Q.10The path difference between the two waves
11
2
sin
p æö
= w-
ç÷
l èø
x
yat and 
22
2
cos
p æö
= w - +f
ç÷
l èø
x
yat is
(a)
2
l
f
p
(b)
22
lp æö
f+
ç÷
p
èø
(c)
2
2
pp æö
f-
ç÷
l
èø
(d)
2 p
f
l
Q.11 A transverse wave is represented by the equation
( )
0
2
sin
p
=-
l
y y vtx , Here v = wave velocity
For what value of , l the maximum particle velocity equal
to two times the wave velocity
(a)
0
2 y l=p (b)
0
/3 y l=p
(c)
0
/2 y l =p (d)
0
y l =p
Q.12 The equation of a plane progressive wave is given by
( ) 0.025sin 100 0.25 . y tx =+
 The frequency of this wave
would be
(a)
50
Hz
p
(b)
100
Hz
p
(c)
100Hz
(d)
50Hz
Q.13 A wave travelling in positive X-direction with A = 0.2m
has a velocity of 360 m/sec. If 
l
= 60m, then correct
expression  for the wave is
(a)
0.2sin26
60
x
yt
éù æö
= p+
ç÷ êú
èø ëû
 (b)
0.2sin6
60
x
yt
éù æö
= p+
ç÷ êú
èø ëû
(c)
0.2sin26
60
x
yt
éù æö
= p-
ç÷ êú
èø ëû
 (d)
0.2sin6
60
x
yt
éù æö
= p-
ç÷ êú
èø ëû
Q.14The equation of a wave is given as
( ) 0.07sin12 3000 = p-p y xt . where x is in metre and t in
sec , then the correct statement is
(a) 1/ 6m, 250 m/s v l== (b) 0.07m, 300m/s av ==
(c) 1500, 200 m/s nv == (d) None
Q.15 The  equation of a progressive wave is given by
( ) 0.5sin 20 400 y xt =- where x and y are in metre and
t is in  second. The velocity of the wave is
(a) 10 m/s (b) 20 m/s (c) 200 m/s (d) 400 m/s
Q.16 There is a destructive interference between the two waves
of wavelength 
l
 coming from two different paths at a
point. To get maximum sound or constructive interference
at that point, the path of one wave is to be increased by
(a)
4
l
(b)
2
l
(c)
3
4
l
(d)
l
Q.17If two waves of same frequency and same amplitude on
superimposition produced a resultant disturbance of the
same amplitude, the waves differ in phase by
(a) p (b)
2 p
/3 (c) p / 2 (d) zero
DPP/ P 29
3
Q.18Equation of motion in the same direction is given by
1
sin( ), y A t kx = w-
2
sin() y A t kx = w - -q .The amplitude
of the medium particle will be
(a) 2 cos
2
A
q
(b)
2 cos A q
(c) 2 cos
2
A
q
(d) 2Acos q
Q.19The amplitude of a wave, represented by displacement
equation 
1
sin cos ytt
ab
1
= w±w will be
(a)
ab
ab
+
(b)
ab
ab
+
(c)
ab
ab
±
(d)
ab
ab
+
Q.20The displacement due to a wave moving in the positive
x -direction is given by 
2
1
(1)
y
x
=
+
at time 
0 t =
and by
2
1
[1 ( 1)]
y
x
=
+-
at 
2 t =
seconds, where x and y are in
metres. The velocity of the wave in m/s is
(a) 0.5 (b) 1 (c) 2 (d)4
DIRECTIONS (Q.21-Q.23) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes : (a) 1, 2 and 3 are correct
(b) 1 and 2 are correct
(c) 2 and 4 are correct
(d) 1 and 3 are correct
Q.21 P , Q and R are three particles of a medium which lie on the
x-axis. A sine wave of wavelength l is travelling through
the medium in the x-direction. P and Q always have the
same speed, while P and R always have the same velocity .
The minimum distance between –
(1) P and Q is l (2) P and Q is l/2
(3) P and R is l/2 (4) P and R is l
Q.22 A wave represented by the given equation
p
Y A sin 10px 15pt
3
æö
= ++
ç÷
èø
, where x is in meter and t is
in second. The expression represents
(1) A wave travelling in the negative X direction with a
velocity of 1.5 m/sec
(2) A wave travelling in the negative X direction with a
wavelength of 0.2 m
(3) A wave travelling in the positive X direction with a
velocity of 1.5 m/sec.
(4) A wave travelling in the positive X direction with a
wavelength of 0.2 m
Q.23 It is usually more convenient to describe a sound wave in
terms of pressure wave as compared to displacement wave
because –
(1) Two waves of same intensity but different frequencies
have different displacement amplitude but same
pressure amplitude
(2) The human ear responds to the change in pressure and
not to the displacement wave.
(3) The electronic detector (microphone) does respond
to the change in pressure but not to the displacement.
(4) None of the above
DIRECTIONS (Q.24-Q.26) : Read the passage given below
and answer the questions that follows :
Sound from a point isotropic source spreads equally in all
directions in homogeneous medium. Therefore its intensity
decreases with square of distance from the source. When
distance between observer and the source changes, apart from
changes in intensity,  the observer listens sound of pitch higher
or lower than actual pitch depending upon the fact that the
distance between the observer and source is decreasing or
increasing respectively. An observer O is at a distance 2R from
centre of a circle of radius R. A point isotropic sound source S
moves on the circle with uniform angular velocity w = p/3 rad/
s.  Initially observer, source and centre of the circle are in same
line.
R=1m
O S C
R
2R
1R
4
DPP/ P 29
Q.24 Starting from initial moment, the source moves through
an angular displacement 180°. Intensity of the sound as
observed by the observer decreases by a factor of –
(a)2 (b)3
(c)4 (d)9
Q.25During a complete round trip of star on the circle, the
observer listens a sound, whose –
(a) wavelength first decreases to a maximum value then
increases to the original value
(b) wavelength first increases to a maximum value then
decreases to the original value
(c) During the first half time wavelength increases then
decreases to the original value
(d) None of the above is correct because in Doppler's
effect, it is the pitch of sound which changes and not
its wavelength, irrespective of motion of source or
observer.
Q.26 Sound emitted by the source at two successive instants t
1
and t
2
 has minimum and maximum observed pitch
respectively, then –
(a)t
1
 = 1s, t
2
 = 5s
(b)t
1
 = 5s, t
2
 = 7s
(c)t
1
 = 7s, t
2
 = 11s
(d)t
1
 = 5s, t
2
 = 11s
DIRECTIONS (Q. 27-Q.29) : Each of these questions contains
two statements: Statement-1 (Assertion) and Statement-2
(Reason). Each of these questions has four alternative choices,
only one of which is the correct answer. You have to select the
correct choice.
(a) Statement-1 is True, Statement-2 is True; Statement-2 is a
correct explanation for  Statement-1.
(b) Statement-1 is True, Statement-2 is True; Statement-2 is
NOT a correct explanation for Statement-1.
(c) Statement -1 is False, Statement-2 is True.
(d) Statement -1 is True, Statement-2 is False.
Q.27 Statement-1 : Particle velocity and wave velocity both are
independent of time.
Statement-2 : For the propagation of wave motion, the
medium must have the properties of elasticity and inertia.
Q.28 Statement-1 : Speed of wave 
Wavelength
Time period
=
Statement-2 : Wavelength is the distance between two
nearest particles vibrating in phase.
Q.29 Statement-1 : Transverse waves are not produced in liquids
and gases.
Statement-2 : Light waves are transverse waves.