A radioisotope has half life of 10 years. What percentage of the original amount of it would you expect to remain after 20 years?

Options

A. 0
B. 12.5
C. 25
D. 8

Answer

C

Explanation

`t_(1//2) = 10` years, `T = 20` year
We know `T = nt_(1//2) implies n = (20)/(10) = 2`
And `N = ((1)/(2))^(n) N_(0)`
`(N)/(N_(0)) = ((1)/(2))^(2) = (1)/(4)`
% of `(N)/(N_(0)) = (1)/(4) xx 100 = 25%`