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According to the Huygens–Fresnel principle , even a very flat plate would still reflect radar waves , though much less than when a signal is bouncing at a right angle .
 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