The selling rate of a radioactive isotope is decided by its activity. What will be the second-hand rate of a one month old 32P (t1/2 = 14.3 days) source if it was originally purchased for 800 rupees?

Given, t1/2 = 14.3 days

The disintegration rate, s-1


t = 1 month = 30 days


A˳ = 800 disintegrations/sec


According to Law of Radioactivity, rate of disintegration of a radioactive isotope at time t will decay exponentially with rate of disintegration initially.


So,



disintegrations/sec


Hence, selling rate will be 187 rupees.


1