# Topic 3 Videos: An Introduction to Diffraction

## Video 3.0: Fourier Series

This video discusses Fourier series and how they can be used to build complex functions from simple periodic functions, like sines and cosines.
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## Video 3.1: General Theory of Diffraction

We discuss the general theory of diffraction and build an expression for intensity which can be tested experimentally. We also build a delta k vector which is critical to our understanding of diffraction.
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## Video 3.2: Scattering Density

We discuss scattering density and create a mathematical description of this concept.
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## Video 3.3: Exploring the Diffraction Equation when ΔK=G

We consider the impact of different source and detector positions (setting delta-K) on the measured intensity. We find the condition for strong constructive interference is the condition that delta-K must equal a G vector of the crystal. Later, we'll show that this is a necessay, but insufficient criteriom when we consider structure factor.

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## Video 3.4: Structure Factor

We now discuss how, given a structure and a basis, we can predict the spacing, position and magnitude of the intensity. We find that, in practice, we have no idea where atoms sit in a lattice. So we take a guess, use the structure factor to calculate the intensity and compare that to experimental data. We also go through the structure factor and how to use it mathematically.
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## Video 3.5: Centered Lattices

We briefly discuss centered lattices and the information they can give us.
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