An electron is travelling with a velocity v in free space and when it enters a medium, its velocity is reduced by 20 %. The de Broglie wavelength of…

An electron is travelling with a velocity $\displaystyle v$ in free space and when it enters a medium, its velocity is reduced by $\displaystyle 20 \%$. The de Broglie wavelength of electron in the medium is $\displaystyle \alpha \lambda_0$, where $\displaystyle \lambda_0$ is its de Broglie wavelength in free space. The value of $\displaystyle \alpha$ is $\displaystyle \_\_\_\_$.