The de-Broglie wavelength associated with an electron and a proton...

$\lambda = \dfrac{h}{mv} = \dfrac{h}{\sqrt{2mK}} = \dfrac{h}{\sqrt{2mqV}}$

$\dfrac{{\lambda}_{1}}{{\lambda}_{2}} = \sqrt{\dfrac{{m}_{2}}{{m}_{1}}}$

$\dfrac{{\lambda}_{e}}{{\lambda}_{p}} = \sqrt{\dfrac{{m}_{p}}{{m}_{e}}} = \sqrt{1831 . 4} = 42 . 79$