24) The half life of a radioactive element is 2 hr and that of the other is 4 hr - Physics - Nuclei

Question

24) The half life of a radioactive element is 2 hr and that of the
other is 4 hr Their initial activities are equal After 4 hrs what
will be the ratio of their activities?
( A )   1   :   2 ( B )   1   :   1 (
C )   1   :   4 ( D )   1   :   3

Aarushi Mishra · Accepted Answer

We knowN=N012n, where n is number of half livesFor first subtanceT1/2)1=2 hours4 hours=2×2 hours=2×T1/2)1N1=N0122N1=N04 ______________1For second subtanceT1/2)2=4 hours4 hours=1×4 hours=1×T1/2)2N2=N0121N2=N02 ______________2Dividing equation 1 and 2N1N2=N04N02=12Ans A

24) The half life of a radioactive element is 2 hr. and that of the other is 4 hr. Their initial activities are equal. After 4 hrs what will be the ratio of their activities? ( A ) 1 : 2 ( B ) 1 : 1 ( C ) 1 : 4 ( D ) 1 : 3

24) The half life of a radioactive element is 2 hr. and that of the other is 4 hr. Their initial activities are equal. After 4 hrs what will be the ratio of their activities?
$(A) 1 : 2 (B) 1 : 1 (C) 1 : 4 (D) 1 : 3$