A parallel beam of electrons travelling in x - direction falls on a slit of width d (see figure). If after passing the slit, an electron acquires momentum p y in the y - direction then for a majority of electrons passing through the slit (h is Planck's constant):

Step-by-step solution

The electron beam will be diffractive at an angle θ For I st minima d sin ⁡ θ =   λ d sin ⁡ θ =   h p Also p sin ⁡ θ = p y ⇒         d   p y = h ∴ majority of electrons passing through the slit are lying in the central maxima d   p y   < h