Waves Ques 39
39. The fundamental frequency of a closed organ pipe of length $20 cm$ is equal to the second overtone of an organ pipe open at both the ends. The length of organ pipe open at both the ends is
[2015]
(a) $100 cm$
(b) $120 cm$
(c) $140 cm$
(d) $80 cm$
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Answer:
Correct Answer: 39.(b)
Solution:
- (b) Fundamental frequency of closed organ pipe,
$v_c=\frac{v}{41_c}$
Fundamental frequency of open organ pipe
$v_0=\frac{v}{2 1_0}$
Second overtone frequency of open organ pipe $=\frac{3 v}{2 l_0}$
From question, $\frac{v}{4 l_c}=\frac{3 v}{2 l_0}$
$\Rightarrow 1_0=61_c=6 \times 20=120 cm$
BETA
