Solution to task 614 from Chertov´s for extramural stud

Solution to task 614 from Chertov´s for extramural stud

614. A parallel beam of monoenergetic electrons falls normally on the diaphragm in the form of a narrow rectangular slit, the width of which is a = 0.06 mm. Determine the speed of these electrons if it is known that on a screen spaced from the slit at a distance of l = 40 mm, the width of the central diffraction maximum is b = 10 μm.