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Derivation of rhkldhkl = λL

Diagram of diffraction of electron beam

From the diagram,

Equation

The Bragg condition (which is true for the sets of variables that produce diffraction spots) states that:

Equation

In electron diffraction, the angle θ is small so that we can make the following approximations:

Equation

with θ in radians. Hence,

Equation

and so it follows that

rhkldhkl = λ L


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