A monoatomic ideal gas, intially at temperature $1_{1}$ is enclosed in a cylinders fitted with a frictionless piston. The gas is allowed to expand adiabatically to a temperature $\mathrm{T}_{2}$ by releasing the piston suddenly If $\mathrm{L}_{1}$ and $\mathrm{L}_{2}$ the lengths of the gas column before and after expansion respectively, then then $\left(\mathrm{T}_{1} / \mathrm{T}_{2}\right)$ is given by
(A) $\left\{\mathrm{L}_{1} / \mathrm{L}_{2}\right\}^{(2 / 3)}$
(B) $\left\{\mathrm{L}_{2} / \mathrm{L}_{1}\right\}^{(2 / 3)}$
(C) $\left\{\mathrm{L}_{1} / \mathrm{L}_{2}\right\}$
(D) $\left\{\mathrm{L}_{2} / \mathrm{L}_{1}\right\}$