question_answer 41)

  The variation of decay rate of two radioactive samples A and B with time is shown in Fig. 8(EP).l1. Which of the following statements are true? a) Decay constant of A is greater than that of B, hence A always decays faster than B b) Decay constant of B is greater than that of  A but its decay rate is always smaller than that of A c) Decay constant of A is greater than that of B but it does not always decay faster than B (d) Decay constant of B is smaller than that of Abut still its decay rate becomes equal to that of A at a later instant

Answer:

  (c,d)From Pig. 8(EP).1, we find that rate of decay of A is faster than that of B. It means decay constant of A is greater than that of B. However, the two curves intersect at P. Beyond P, B decays faster than A. And at P, decay rate of both A and B is the same. Hence, choices (c) and (d) are correct