A U-tube manometer of tube diameter $D$ is filled with a liquid of zero viscosity. If the volume of the liquid filled is $V$, the natural frequency of oscillations in the liquid level about its mean position, due to small perturbations, is
- $\frac{D}{2\sqrt{2\pi}}\sqrt{\frac{g}{V}}$
- $\frac{2\sqrt2}{\sqrt\pi}$$\frac{\sqrt{gV}}{D^2}$
- $\frac{1}{2\sqrt\pi}$$\frac{\sqrt{gD}}{V^{1/3}}$
- $\frac{1}{\sqrt{\pi}}\sqrt{\frac{g}{D}}$