A cylindrical tube open at both ends has a fundamental fruquency f in air. The tube is dipped vertically in water so that 60% of the tube is in water. Then , the fundamental frequency of air column is

Options

A. `(f)/(2)`
B. `(5f)/(4)`
C. `(3f)/(4)`
D. 2f

Answer

B

Explanation

Let us assume the length of tube is L.
It is opn organ pipe, so fundamental frequency,
`f = (V)/(2L)`
If the 60% of tube is dipped vertically in water as shown in the figure.
Now, it is a closed organ pipe of length,
`l.=(40)/(100) xx L = (2L)/(5)`
`:.` Fundamental frequency of air column is `f.=(V)/(4l.)`
`rArr f.=(V)/(4((2L)/(5)))`
`rArr f. = (5)/(40 ((V)/(2L))`
`rArr f. = (5)/(4) xx f or f. = (5f)/(4)`