Understanding the Ewald Sphere

This lecture covers the concept of the Ewald sphere and its interaction with the reciprocal lattice to explain 2-beam electron diffraction in Transmission Electron Microscopy. The instructor introduces the basics of electron diffraction, explains the elastic scattering involved in diffraction events, and details the exact Bragg condition when the scattering wave vector intersects a reciprocal lattice node. Realistic representations of the Ewald sphere are provided, illustrating its flatness and its interaction with crystals and planes. The lecture concludes with a summary of the Ewald sphere, emphasizing the Bragg condition and its application to 2-beam diffraction.