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

Options

A. `f//2`
B. `3f//4`
C. f
D. `2 f`

Answer

C

Explanation

Case I Here `lamda//2 = l`
`:. lamda = 2 l`
Now, `v = f xx lamda`
`:. f = (v)/(lamda) = (v)/(2 l)` ….(i)
Case II Here `lamda'//4 = l//2`
`:. lamda' = 2 l`
Now, `v = f' xx lamda'`
`:. f' = (v)/(lamda') = (v)/(2l) = f`.