616. A stream of monoenergetic electrons is directed from the cathode tube to the diaphragm with a narrow rectangular slit normal to the plane of the diaphragm. Determine the anode voltage of the tube, if it is known that on a screen spaced from the slot at a distance of l = 0.5 m, the width of the central diffraction maximum is Δx = 10.0 μm. The width b of the slot is taken equal to 0.10 mm.