Answer
When accelerating an electron from rest through an electric potential difference, increasing the potential difference will result in a shorter de-Broglie wavelength.
Work Step by Step
From equation 28.3 it is clear that for nonrelativistic electron initially at rest.
de-Broglie wavelength is given by
$\lambda= \sqrt \frac{h^2}{2meV}$,
where $h$ is planks constant, $m$ is mass of electron, $e$ is charge of electron and $V$ is accelerating electric potential difference.
so de Broglie wavelength is inversely proportional to applied electric potential difference.
So increasing the electric potential difference will result in shorter de Broglie wavelength.
