SINGLE SLIT AND GRATING
Dark bands found at sinθ = mλ/a.





Note that for a single slit, the width of the central maximum is inversely proportional to the slit width.
I(φ) = I₀[[sin(φ/2)]/[φ/2]]². Here, φ is the phase angle, φ = 2πδ/λ, with δ the usual path difference.

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The Rayleigh Criterion for Resolution

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DIFFRACTION GRATING-- transparent plate with parallel scratches



sinθ_b,m = mλ/d.


Diffraction of X-ray photons or electrons from crystals or molecules produces a pattern which can be inverse-transformed to show the electron density distribution from which the particles scattered.  Using computer programs that calculate the electron density, based on given atomic arrangements, it is possible to obtain very detailed information about precisely how atoms are fitted together in complex crystals or molecules.
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