Using the relation.
$ {{T}_{1}}{{V}_{1}}^{\gamma -1}={{T}_{2}}V_{2}^{\gamma -1} $
$ \frac{{{V}_{2}}}{V}={{\left( \frac{{{T}_{1}}}{{{T}_{2}}} \right)}^{1-\gamma }}={{\left( \frac{{{T}_{1}}}{2{{T}_{1}}} \right)}^{1-\gamma }} $
Or $ \frac{1}{{{(2)}^{1-\gamma }}}>\frac{1}{2} $