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Initially it was thought to be high-energy gamma radiation , since gamma radiation had a similar effect on electrons in metals , but James Chadwick found that the ionization effect was too strong for it to be due to electromagnetic radiation , so long as energy and momentum were conserved in the interaction .
 person: James Chadwick
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
 Entities: James Chadwick 
Answer:
 person: James Chadwick