Wave Motion 2 Question 10
10. A pipe open at both ends has a fundamental frequency $f$ in air. The pipe is dipped vertically in water, so that half of it is in water. The fundamental frequency of the air column is now
(2016 Main)
(a) $\frac{f}{2}$
(b) $\frac{3 f}{4}$
(c) $2 f$
(d) $f$
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Answer:
Correct Answer: 10. (d)
Solution:
- Fundamental frequency of open pipe.
$$ f=\frac{v}{2 l} $$
Now, after half filled with water it becomes a closed pipe of length $\frac{l}{2}$.
Fundamental frequency of this closed pipe,
$$ f^{\prime}=\frac{v}{4(l / 2)}=\frac{v}{2 l}=f $$
