The de Broglie wavelength for an electron accelerated through the potential difference of V_1 volt is λ_1. When the potential difference is changed…

The de Broglie wavelength for an electron accelerated through the potential difference of $\displaystyle V_1$ volt is $\displaystyle \lambda_1$. When the potential difference is changed to $\displaystyle V_2$ volt, the associated de Broglie wavelength is increased by $\displaystyle 50 \%$. If $\displaystyle \left(V_1 / V_2\right)=(9 / \alpha)$, then the value of $\displaystyle \alpha$ is $\displaystyle \_\_\_\_$.