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The decay constant of a radio isotope is λ. If A1 and A2 are its activities at times t1 and t2 respectively, the number of nuclei which have decayed during the time (t1 – t2) :
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- λ (A1 - A2)
- A1t1 - A2t2
- A1 - A2
- (A1 - A2)/λ
Correct Option: D
Activity is given by
| A = | - λN | |
| dt |
A1 = -λ N1
and activity at time t2 is A2 = – l N2 As t1 > t2 , therefore, number of atoms remained after time t1 is less than that remained after time t2 . That is, N1 < N2 .
∴ number of nuclei decayed in (t1 – t2)
| = N2 - N1 = | ||
| λ |
