Relating to or caused by diffraction; concerning the bending or spreading of waves around obstacles.
From 'diffraction' plus the adjective suffix '-al.' It's the adjectival form that modifies nouns relating to the physical phenomenon of wave-bending.
Physicists use 'diffractional analysis' to study the atomic structure of crystals by shooting X-rays through them and analyzing how the diffracted rays create patterns—this is how we discovered the shape of DNA molecules!
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