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X-ray Diffraction

X-ray Wave Interference

Constructive vs. Destructive Wave Interference

When x-ray waves interact, they sum together to create either amplified waves (constructive interference) or suppressed waves (destructive interference).

The interference type depends on the phase of the x-rays (i.e., if the wave peaks are in or out of phase with each other).

Constructive vs Destructive
In phase (peaks aligned) compared to out of phase (peaks not aligned).

Scattering  

When an x-ray wave interacts with individual atoms, it can be absorbed by the electrons and cause the electrons to oscillate (wiggle). This oscillation acts as a new emission source and emits an x-ray of the same energy as the incident x-ray. This is known as Thomson scattering.

All of the individual sources of scatter will subsequently constructively and destructively interfere with each other, creating a diffraction pattern.

Scattering diagram