The gamma ray released by each decay carries 140kev of energy. find the total energy e released by decays in the 2 hours.

First, we would need to know the decaying isotope.

Next, we use the decay formula

A = Ao e^ (-kt)

After determining the remaining amount after two hours, the decay reaction can be used to determine the number of gamma rays released. If the given is in terms of mole, then the total energy is

E = 140n KeV where n is the number of moles of gamma rays released