In a throttling process, the pressure of an ideal gas reduce by $50\%$. If $C{_p}$ and $C{_v}$ are the heat capacities at constant pressure and constant volume, respectively ($\gamma = C{_p}/C{_v}$), the specific volume will change by a factor of

1. $2$
2. $2^{1/\gamma}$
3. $2^{({\gamma – 1})/\gamma}$
4. $0.5$