Obtain the amount of ⁶⁰₂₇Co necessary to provide a radioactive source of 8.0 mCi strength. The half-life of ⁶⁰₂₇Co is 5.3 years.

The Strength a radioactive element is given by =

And, 1Ci = 3.7 × 10¹⁰decays/sec;

∵ hence, 8.0 mCi = 8 × 10^-3 × 3.7 × 10¹⁰

= 29.6 × 10⁷ decay/sec (∵ 1 Ci = 3.7 × 10¹⁰ decay/sec)

Half life of Co⁶⁰ is 5.3 years

= 5.3 × 365 × 86400 sec (∵ 1day = 86400 sec)

= 1.67 × 10⁸ s^-1

We know,

N = =

Mass of 7.133 × 10¹⁶ atoms will be = gms

Hence, we need gms of Co⁶⁰.