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In 1666 Isaac Newton , based on his theories of refraction and color , perceived that the faults of the refracting telescope were due more to a lens 's varying refraction of light of different colors than to a lens 's imperfect shape .
 Isaac Newton
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
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Text: {0} 
Answer:
 Isaac Newton