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In classical physics diffraction arises because of the way in which waves propagate ; this is described by the Huygens–Fresnel principle and the principle of superposition of waves .
 person: Huygens–Fresnel
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 person: Huygens–Fresnel