Why were Japanese placed in internment camps during world war ll?

Well a brief explanation is because people in America thought that some Japanese Americans could be spies or affiliated with the Japanese government in any way and didn't want to take any chances, so the Japanese Americans were taken to internment camps during world war 2

Mass fear and paranoia. Americans grew fearful that they would side with Japan in the war even though there was no specific evidence that Japanese-Americans posed a danger to American security. The Court justified the policy as a military necessity in wartime.