The best replacement for diffraction is interference.

The best alternatives to diffraction are rated as following:
★★★★★  interference
★★★★★  refraction
★★★  scattering
★★★  dispersion
★★  reflection
★  depth of field
★  dof
★  refraction physics
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  electron diffraction
  x-ray fluorescence

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Speaking about diffraction, one probably shouldn't forget about interference.

Other search terms related to diffraction and their ratings are:
★★★★★ interference
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