(2) A small Quantity of solution containing Na-24 radioactive nuclei
t1/2 = 15h of activity 1.0  ci is injected into the blood of a person. A sample of blood of volume 1cm3 taken after 5th, throws an activiy of 296 d/ min.
Determine the total voume of blood in the body of person
Let volume of blood be V
activity of 1 cm3 initially = 
activity after 5 hrs = A1 =  = 4.93 dps
(3)  Polinum is used forgeneration of electricity, assuming the efficiency of the electricity, assuming the efficiency of the electric machine to be 10% how much P0 is required 693 days. Also find the intial activity of material.
(mass of nucleii P0 - 210 = 209.98264 u Ph - 206 = 205.97440 u 2He4 = 4.00260 u)
mass defect = (209.98264) - (205.97440 + 4.00260) = 000564u = 5.64 x 10-3 x 931Mev = 8.34 x 10-3J.
No. of fissions required for 1.2 x 107J =  = 1.43 x 1019
Since efficiency of machine is 10%
 Actually no. of fissions occuring = 1.43 x 1019 x 10 = 1.43 x 1020
mass of polinium required =  x 210 = 0.0485g
at the end of 693days 0.0483g of P0 must be present
693 days = 138.6 x 5 = 5 x t1/2
intial mass of polinium = 0.0483 x 25 = 0.0483 x 32 = 1.5456g
intial activity =...N0=.....X 1.43 x 1020 x 32
= 2.2 x 1019/day
Hard:
1. Nuclei of a radio active element A are being produced at a constant rate  . The element has a decay constant  . At time t = 0, there are N0 nuclei of the element.
(a) Calculate the number No of Nuclei of A at time t.
(b) If  after half life of a , and also the limiting value of Nas t  
Solution:- Rate of production =
rate of decay = [n]
 integrating
 (Ans to (a) part)
at t = 
limiting value i.e. as t
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