The half-life of radium is about `1600 yr`. Of `100g` of radium existing now, `25 g` will remain unchanged after

Options

A. 6400 years
B. 2400 years
C. 3200 years
D. 4800 years

Answer

C

Explanation

`{:(M_0=100g,"(initial mass )"),("M=25g","(active mass)"):}}rArrN_0/N=100/25`
`Delta=2^2rArr n=2`
Therefore required time =`2xxT_(1//2)`=3200 yrs