Phonon scattering

Phonon scattering is like when a stone is thrown into a pond. The stone makes waves that bounce off the sides of the pond and cause ripples to travel around in all directions. Phonons are like these tiny ripples that travel through material like rocks and metals. When they hit something in the material, like an atom or nucleus, they can scatter, or bounce off in a different direction. This can slow down the speed of the phonons, just like the ripples in the pond slow down as they travel away from the original impact point.