Question
Question: A and B are two radioactive substances whose half lives are 1 and 2 years respectively. Initially 10...
A and B are two radioactive substances whose half lives are 1 and 2 years respectively. Initially 10 gm of A and 1 gm of B is taken. The time (approximate) after which they will have same quantity remaining is –
A
6.62 years
B
5 years
C
3.2 years
D
7 years
Answer
6.62 years
Explanation
Solution
MA= MB Ž 2t/110 = 2t/21 Ž 2t/2 = 10
log10 2 t/2 = log10 10 Ž 2t log10 2 = 1
t = log1022 = 6.62 years