Question

A cylindrical tube, open at both ends, has a fundamental frequency in air. The tube is dipped vertically in water so that half of its length is in water. The fundamental frequency of the air column is now

• A. f/2
• B. 3f/4
• C. f
• D. 2f

Answer 1

Answer: (C)

For the cylindrical tube open at both ends, $f=v/2l$.
When half of the tube is in water, it behaves as a closed pipe of length $l/2$.
$\therefore f^{\prime }=\frac{v}{4(l/2)}=\frac{v}{2l}$
$\therefore f^{\prime }=f\text{. }$