A nuclear power plant supplying electrical power to a village uses a radioactive material of half life T years as the fuel. The amount of fuel at the beginning is such that the total power requirement of the village is 12.5 of the electrical power available from the plant at that time. If the plant is able to meet the total power needs of the village for a maximum period of nT years, then the value of n is
Initially the radioactivity of the plant is A0 and power requirment of the town is A.
So the power devloped by the plant to match the town power;
A08=A0e−λt⇒A02t/T
A08=A02t/T
8=2t/T23=2t/T
So, ⇒3=tTt=3T
Hence the value of n=3.