Waves Ques 42
42. The number of possible natural oscillation of air column in a pipe closed at one end of length $85 $ $cm$ whose frequencies lie below $1250 $ $Hz$ are : (velocity of sound $=340 $ $ms^{-1}$ )
[2014]
(a) $4$
(b) $5$
(c) $ 7$
(d) $6$
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Answer:
Correct Answer: 42.(d)
Solution:
- (d) In case of closed organ pipe frequency,
$f_n=(2 n+1) \frac{v}{4 l}$
for $n=0, f_0=100 $ $Hz$
$n=1, f_1=300 $ $Hz$
$n=2, f_2=500 $ $Hz$
$n=3, f_3=700 $ $Hz$
$n=4, f_4=900 $ $Hz$
$n=5, f_5=1100 $ $Hz$
$n=6, f_6=1300 $ $Hz$
Hence possible natural oscillation whose frequencies $<1250 $ $Hz=6(n=0,1,2,3,4,5)$
BETA
