Co-57 decays to Fe-57 by beta positive emission. The resulting Fe-57 is in its excited state and comes to the ground state by emitting gamma rays.The half life of beta positive decay is 270 days of and that of Gamma emission is 10^-8 s. A sample of Co-57 gives 5×10^9 gamma rays per second. How much time will elapse before the emission rate of Gamma rays drops to 2.5×10^9 per second?

Vidhi dixit , 5 Years ago

Grade 12th pass