Question

the T 1/2 of a certain radioisotope is 4 weeks what fraction of the original isotope remains after 12 weeks​

Answer 1

The fraction of original isotope remaining after 12 weeks is 1/8 (0.125)

Step-by-step explanation:

The half life of the radio-isotope = 4 weeks =
`t_{(1)/(2)}`

After n half lives, the fraction of original isotope remaining =
`(1)/(2^(n))`

In 12 weeks, the number of half lives = 12/4 = 3 half lives

The fraction of original isotope remaining =
`(1)/(2^(3))=(1)/(8)`

Hence, after 12 weeks, fraction of original isotope remaining is 1/8 (0.125)