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(i) Define ‘activity’ of a radioactive material and write its SI unit. (ii) Plot a graph showing variation of activity of a given radioactive sample with time. (iii) The sequence of stepwise decay of a radioactive nucleus is Doverset(alpha)(to)D_(1)overset(beta^(-))D_(2) If the atomic number and mass number of D_(2) are 71 and 176 respectively, what are their corresponding values for D? |
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Answer» Solution :(i) The activity or the rate of decay (R) of a radioactivesample is defined as the number of disintegrationstaking place per unit TIME in given sample. `THEREFORE` Activity `R=-(dN)/(dt)=lambdaN=lambdaN_(0)e^(-lambdat)` SI unit of activity is `("second")^(-1) or s^(-1)`.  (ii) A graph showing variation of activity of a given radioactive sample with time is given in FIG. 13.07. (iii) The sequence of decays may be expressed as `" "_(72)^(180)D overset(alpha)underset(" "_(2)^(4)He)(to)" "_(70)^(176)D_(1)overset(beta^(-))underset(" "_(-1)^(0)e)(to)" "_(71)^(176)D_(2)` Thus, atomic number and mass number of D are 72 and 180 RESPECTIVELY. |
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