Question

The decay constant of a radioisotope is lambda if a1 and a2 are its activities at times t1 and t2 respectively

Answer 1

The decay constant of a radio isotope is λ if a1 and a2 are

its activities at times t1 and t2 respectively no of nuclei which have decayed

during the time( t1-t2)  .

find (t1-t2)=?

so A1=lambda N1 at time t1=λN1

 A2 =lambda N2 at time t2=λN2

therefore no of nuclei  decayed during time interval (t1-t2)

λN1-λN2=A1-A2

λ taking common so

λ(N1-N2)=A1-A2

⇒N1-N2=A1-A2/λ  

hence answer is