(i) Define 'activity' of a radioactive material and write its S.I. 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 D overset(alpha) (to) D_(1) overset(beta-) (to) D_(2) If the atomic number and mass number of D_(2) are 71 and 176 respectively, what are their corresponding values for D ?

(i) Define 'activity' of a radioactive material and write its S.I. uni

1.	(i) Define 'activity' of a radioactive material and write its S.I. 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 D overset(alpha) (to) D_(1) overset(beta-) (to) D_(2) If the atomic number and mass number of D_(2) are 71 and 176 respectively, what are their corresponding values for D ?
Answer» Solution :(i) The total decay rate (of a SAMPLE) at the given instant i.e. the number of radio-nuclides DISINTEGRATING per unit TIME is CALLED the activity of that sample. The SI unit for activity is becquerel (Bq). (ii) Graph: (III) `72 and 180`.

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