An electron and a proton have the same kinetic energy and are moving at speeds much less than the speed of light. Concepts: (i) How is the de Broglie wavelength l related to the magnitude p of the momentum? (ii) How is the magnitude of the momentum related to the kinetic energy of a particle of mass m that is moving at a speed that is much less than the speed of light? (iii) Which has the greater de Broglie wavelength, the electron or the proton? Calculations: Determine the ratio of the de Broglie wavelength of the electron to that of the proton.