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Class 11 NEET Physics Waves Questions Questions
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© examsnet.com
Question : 52
Total: 91
A car is moving towards a high cliff. The driver sounds a horn of frequency
f
. The reflected sound heard by the driver has frequency
2
f
.
If
v
is the velocity of sound, then the velocity of the car, in the same velocity units, will be
(2004)
v
√
2
v
3
v
4
v
2
Validate
Solution:
1
st
the car is the source and at the cliff, one observes
f
′
.
∴
f
′
=
v
v
−
v
s
f
2
nd
cliff is now source. It emits frequency
f
′
and the observer is now the driver who observes
f
"
.
∴
f
"
=
[
v
+
v
o
v
]
f
′
or
2
f
=
[
v
+
v
o
v
−
v
s
]
f
⇒
2
v
−
2
v
o
=
v
+
v
o
[ as
v
s
=
v
o
]
⇒
v
o
=
v
3
© examsnet.com
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