A Level Physics Practice Exam 2025 - Free A Level Physics Practice Questions and Study Guide

The phenomenon that explains electron diffraction through an atomic lattice is particle-wave duality. This concept arises from quantum mechanics and suggests that particles, such as electrons, exhibit both particle-like and wave-like properties. When electrons pass through an atomic lattice, they can be treated as waves, which allows them to undergo diffraction, similar to how light waves interact with a diffraction grating.

In this context, as the electron waves interact with the regular arrangement of atoms in the lattice, they can constructively or destructively interfere, leading to the pattern known as a diffraction pattern. This behavior is fundamentally rooted in the wave nature of electrons, and it demonstrates how quantum mechanics applies to particles on a very small scale.

The other options mentioned do not directly explain this phenomenon. The photoelectric effect describes the emission of electrons from a material when light is incident upon it and does not involve diffraction. Brownian motion deals with the random movement of particles suspended in a fluid and is unrelated to electron behavior in a lattice. Quantum tunneling refers to the process by which particles can pass through barriers that they classically would not be able to surmount, but it does not describe the phenomena observed in diffraction.