10

WAVES
Page
1
( Answers
at
the
end
of
all
questions )
1 )
When
two
tuning
forks
( fork
1
and
fork
2 )
are
sounded
simultaneously,
4
beats
per
second
are
heard.
Now,
some
tape
is
attached
on
the
prong
of
fork
2.
When
the
tuning
forks
are
sounded
again,
6
beats
per
second
are
heard.
If
the
frequency
of
fork
1
is
200
Hz,
then
what
was
the
original
frequency
of
fork
2 ?
( a )
202 Hz
( b )
200
Hz
( c )
204
Hz
( d )
196
Hz
[ AIEEE
2005 ]
2 )
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 ?
3 )
The
displacement
y
of
a
particle
in
a
medium
can
be
expressed
as
y
=
10

6
sin ( 100t
+
20x
+
π
/
4 )
m,
where
t
is
in
second
and
x
in
metre.
The
speed
of
the
wave
is
4 )
The
displacement
y
of
a
wave
travelling
in
the
x
–
direction
is
given
by
y
=
10

4
sin ( 600t

20x
+
π
/
3 )
metres,
where
x
is
expressed
in
metres
and
t
in
seconds.
The
speed
of
the
wave
motion
is
5 )
A
tuning
fork
of
frequency
256
Hz
makes
5 beats
per
second
with
the
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
piano
string
before
increasing
the
tension
was
( a )
( 256 + 2 ) Hz
( b )
( 256 + 5 ) Hz
( c )
( 256

2 ) Hz
( d )
( 256

5 ) Hz
[ AIEEE
2003 ]
6 )
The
displacement
of
a
wave
is
given
by
the
equation
y
=
2 sin (
π
/
1.6 ) ( 64t

x
).
The
frequency
of
the
wave
is
7 )
Transverse
are
generated
in
two
uniform
wires
A
and
B
by
attaching
their
free
ends
to
a
vibrating
source
of
frequency
600
Hz.
The
diameter
of
wire
A
is
onethird
that
of
wire
B
and
tension
in
the
wire
A
is
double
that
in
wire
B.
What
is
the
ratio
of
velocities
of
waves
of
waves
in
wire
A
and
B ?
8 )
If
the
phase
difference
between
two
points
is
60
°
on
a
wave
velocity
of
360
m
/
s
and
frequency
500 Hz,
then
path
difference
between
the
two
points
is
9 )
A
resonance
air
column
of
length
40
cm
resonates
with
a
tuning
fork
of
frequency
450
Hz.
Ignoring
end
correction,
the
velocity
of
sound
in
air
will
be
( a )
720
m
/
s
( b )
820
m
/
s
( c )
920
m
/
s
( d )
1020
m
/
s
[ AIEEE
2002 ]
10 )
An
observer
is
moving
towards
a
stationary
source
of
frequency
250
Hz
with
a
velocity
of
40
m
/
s.
If
the
velocity
of
sound
is
330
m
/
s,
the
apparent
frequency
heard
by
the
observer
will
be
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10

WAVES
Page
2
( Answers
at
the
end
of
all
questions )
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 Spring '06
 Jones
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