Wave Nature Of Matter

The fringe width in a Young's double-slit experiment is given by the formula:
where
is the wavelength of the particles (electrons or protons),
is the distance between the slits and the screen, and
is the slit separation.

Since the wavelength of a particle depends on its momentum, the electron, being lighter, has a longer de Broglie wavelength than the proton. Therefore, the fringe width for the electron beam will be greater than that for the proton beam ,
i.e., .