This document provides solutions to two physics problems involving the de Broglie relation between particle momentum and wavelength: 1) Estimating the kinetic energy of electrons in an electron microscope to resolve a 0.27 nm separation. The solution is 15.37 MeV. 2) Estimating the crystal planar separation from a scattering experiment observing the fifth intensity maximum of 2 eV protons scattered at 300. The solution is 0.1026 nm.