Half life of a radio active element is 1200 yrs. It m0 gm of radio active element existing now, m0/4 gm will remain radio active after
600 years
4800 years
2400 years
2800 years
NN0=1(2)t/T⇒m0/4m0=1(2)t/T⇒1(2)2=1(2)t/T
⇒t/T=2⇒t=2×1200 years
= 2400 years