An electron microscope uses electrons of energy 2 keV. What is the approximate size of the smallest structures that can be resolved?

NOTE: At 1:38 in the video, Prof. Bowen writes $v = \sqrt{2Km}$, but it should be $v = \sqrt{2K/m}$. But his calculations are correct -- the speed that he gets uses the correct result ($v = \sqrt{2K/m}$).