A cylindrical tube open at both the ends has a fundamental frequency of 390 Hz in air. If `1/4` th of the tube is immesed vertically in water the fundamental frequency of air column is

Options

A. 260 Hz
B. 130 Hz
C. 390 Hz
D. 520 Hz

Answer

d

Explanation

Fundamental frequency of cylindrical open tube

`n=v/(2L) = 390` Hz
When it is immersed in water it becomes a closed tube of
length `3/4`th of the initial length.
Therefore, its fundamental frequency is
`n'=v/(4(3/4L))=v/(3L)=2/3(v/(2L))=2/3xx 390 Hz = 260 Hz`