The count rate of an alpha-particle source is 400 per minute. If the half-life of the source is 5 days, what would be the count rate per minute after 15 day...

The count rate of an alpha-particle source is 400 per minute. If the half-life of the source is 5 days, what would be the count rate per minute after 15 days?

Answer Details

The count rate of an alpha-particle source refers to the number of alpha particles emitted by the source in one minute. The half-life of a radioactive source is the time it takes for half of the radioactive atoms to decay. If the count rate of the alpha-particle source is 400 per minute and the half-life of the source is 5 days, this means that after 5 days, the count rate will decrease to 200 per minute (half of 400). After another 5 days (a total of 10 days), the count rate will decrease to 100 per minute (half of 200). After another 5 days (a total of 15 days), the count rate will decrease to 50 per minute (half of 100). Therefore, the count rate per minute after 15 days will be 50, and the correct answer is option (C) 50.