The Complementarity Principle
Is an electron a particle -- like a tiny bee-bee? The photoelectric effect tends to indicate that it is.
Is an electron a wave -- like sound or water waves? Electron diffraction from crystals indicates that it is.
Actually, we will need both descriptions. And this dual nature of the Universe will be with us throughout our study of atomic and nuclear and particle Physics -- as it was in our study of optics!
Our "particle model" and our "wave model" seem to be contradictory. This disturbed the best and brightest minds in Science for the first three or four decades of the twentieth century (and the conflict had been around since 1801 with Young's double slit experiment in optics!). It remained for the great Danish Physicist, Niels Bohr, to propose that these ideas were not contradictory. Rather, Bohr argued, they are complementary -- both models are necessary!
deBroglie Waves Probabilities Return to Ch 28, Quantum Mechanics (c) Doug Davis, 2002; all rights reserved