Diffraction Patterns of Light and Particles

Energy and mass exhibit properties that in classical mechanics are exclusive of each other.

Just as light is scattered after passing through a narrow medium, particles experience the same phenomenon. Miraculously, when a particle is observed is is seen to go through only one diffraction slit even though experimentally it has the same diffraction pattern as if it passed through both slits of a double slit experiment at the same time. A mystery of modern physics.