Problem 6.58

A parallel stream of monoenergetic electrons falls normally on a diaphragm with narrow square slit of width \(b=1.0 \mu \mathrm{m}\). Find the velocity of the electrons if the width of the central diffraction maximum formed on a screen located at a distance \(l=50 \mathrm{~cm}\) from the slit is equal to \(\Delta x=0.36 \mathrm{~mm}\).