Question

A radioactive isotope has a half life of 40 days .What is the time required for the activity of the isotope to fall to 1/8 th of its original value

Answer 1

Answer:

Half-life (t½) is the amount of time required for a quantity to fall to half its value as measured at the beginning of the time period.

Answer 2

Explanation:

In this question (t½) of isotope is 100 years, which means that after 100 years half of the sample would have decayed and half would be left as it is.

After 100 years ( first half life) 40 /2 = 20 g decays and 20 g remains left.

After another 100 years ( two half lives or 200 years) 20 /2 = 10 g decays and 10 g remains left .

after two half lives or 200 years, 10 g of the isotope will be left.