A radioisotope has half life of 10 years. What percentage of the original amount of it would you expect to remain after 20 years? a)0 b)12.5 c)25 d)8

Options

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

Answer

C

Explanation

` t_(1//2)= 10 year , 20 year `
We kinow ` T= nt_(1//2) rArr n= (20)/(10) =2`
and `N= (1/2)^n N_0 rArr N/N_0 (1/2)^2 = 1/4`
` %of = (1/2)^n 1/4 xx 100 = 15%`.