- 
					 The half life of a radioactive nucleus is 50 days. The time interval (t2 – t1 ) between the time t2 when 2/3 of it has decayed and the time t1 when 1/3 of it had decayed is :
 
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- 30 days
 - 50 days
 - 60 days
 - 15 days
 
 
Correct Option: B
N1 = N1  e–λt
| N1 = | N0 | |
| 3 | 
| = N0e- λt2 | ||
| 3 | 
| = e- λt2 ....(i) | ||
| 3 | 
| N2 = | N0 | |
| 3 | 
| N0 = N0e- λt1 | ||
| 3 | 
| = e- λt1 | ||
| 3 | 
Dividing equation (i) by equation (ii)
| = e- λ(t2 - t1) | ||
| 2 | 
λ(t2 - t1) In 2
| t2 - t1 = | = T1/2 = 50 days | |
| λ |