Nuclei - Result Question 77

78. In a radioactive material the activity at time t1 is R1 and at a later time t2, it is R2. If the decay constant of the material is λ, then

[2006]

(a) R1=R2eλ(t1t2)

(b) R1=R2e(t2/t1)

(c) R1=R2

(d) R1=R2eλ(t1t2)

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Answer:

Correct Answer: 78. (d)

Solution:

  1. (d) Let at time Misplaced &, number of particles be Misplaced &. So,

R1=dN1dt=λN1;R2=dN2dt=λN2

R1R2=λN1λN2=N1N1eλ(t2t1)=eλ(t2t1)

R1=R2eλ(t2t1)=R2eλ(t1t2)



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