Question

A cylindrical resonance tube open at both ends, has a fundamental frequency $$f,$$ in air. If half of the length is dipped vertically in water, the fundamental frequency of the air column will be

A. $$2f$$
B. $$\frac{{3f}}{2}$$
C. $$f$$  
D. $$\frac{{f}}{2}$$
Answer :   $$f$$
Solution :
Fundamental frequency of open pipe,
\[f = \frac{v}{{2l}}\,.......\left( {\text{i}} \right)\,\,\left[ {\begin{array}{*{20}{c}} {v = {\text{velocity of wave}}} \\ {l = {\text{length of open pipe}}} \end{array}} \right]\]
When half length of tube is dipped vertically in water, then length of the air column becomes half $$\left( {l' = \frac{l}{2}} \right)$$  and the pipe becomes closed.
So, new fundamental frequency of closed pipe
$$f' = \frac{v}{{4l}} = \frac{v}{{4\left( {\frac{l}{2}} \right)}} = \frac{v}{{2l}}\,.......\left( {{\text{ii}}} \right)$$
From Eqs. (i) and (ii), we get,
$$f' = f$$
Hence, there will be no change in fundamental frequency.

Releted MCQ Question on
Oscillation and Mechanical Waves >> Waves

Releted Question 1

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

A. $$\frac{f}{2}$$
B. $$\frac{3\,f}{4}$$
C. $$f$$
D. $$2\,f$$
Releted Question 2

A wave represented by the equation $$y = a\cos \left( {k\,x - \omega t} \right)$$    is superposed with another wave to form a stationary wave such that point $$x = 0$$  is a node. The equation for the other wave is

A. $$a\sin \left( {k\,x + \omega t} \right)$$
B. $$ - a\cos \left( {k\,x - \omega t} \right)$$
C. $$ - a\cos \left( {k\,x + \omega t} \right)$$
D. $$ - a\sin \left( {k\,x - \omega t} \right)$$
Releted Question 3

An object of specific gravity $$\rho $$ is hung from a thin steel wire. The fundamental frequency for transverse standing waves in the wire is $$300\,Hz.$$  The object is immersed in water so that one half of its volume is submerged. The new fundamental frequency in $$Hz$$  is

A. $$300{\left( {\frac{{2\,\rho - 1}}{{2\,\rho }}} \right)^{\frac{1}{2}}}$$
B. $$300{\left( {\frac{{2\,\rho }}{{2\,\rho - 1}}} \right)^{\frac{1}{2}}}$$
C. $$300\left( {\frac{{2\,\rho }}{{2\,\rho - 1}}} \right)$$
D. $$300\left( {\frac{{2\,\rho - 1}}{{2\,\rho }}} \right)$$
Releted Question 4

A wave disturbance in a medium is described by $$y\left( {x,t} \right) = 0.02\cos \left( {50\,\pi t + \frac{\pi }{2}} \right)\cos \left( {10\,\pi x} \right)$$        where $$x$$ and $$y$$ are in metre and $$t$$ is in second

A. A node occurs at $$x = 0.15\,m$$
B. An antinode occurs at $$x = 0.3\,m$$
C. The speed wave is $$5\,m{s^{ - 1}}$$
D. The wave length is $$0.3\,m$$

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Waves


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