Waves - Result Question 45
47. 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: 47. (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 $<1250 Hz=6(n=0,1,2,3,4,5)$
