CBSE · Class 12 · Physics · NucleiExplain the phenomenon of nuclear fission with a suitable example and state how energy is released in the process.

Nuclear fission is defined as a nuclear reaction in which a heavy nucleus, such as uranium or plutonium, splits into two or more smaller, comparable lighter nuclei accompanied by the release of a massive amount of energy and typically a few neutrons. \nWhen a thermal neutron is absorbed by a uranium-235 ($^{235}_{92}\text{U}$) nucleus, it forms an unstable compound nucleus of uranium-236, which immediately breaks apart. A classic example of nuclear fission is the bombardment of Uranium-235 by a neutron:

$$^{235}{92}\text{U} + ^1_0\text{n} \rightarrow [^{236}{92}\text{U}] \rightarrow ^{141}{56}\text{Ba} + ^{92}{36}\text{Kr} + 3 ^1_0\text{n} + \text{Energy}$|

Reason for Energy Release:\nThe total binding energy per nucleon of the product nuclei (Barium and Krypton) is higher than that of the original heavy parent nucleus (Uranium). Because the total mass of the products is slightly less than the total mass of the reactants, this "mass defect" ($\Delta m$) is converted directly into energy according to Einstein's mass-energy equivalence equation ($E = \Delta m \cdot c^2$). On average, a single fission of Uranium-235 releases about 200 MeV of energy, making it an extremely potent power source for nuclear reactors and weapons.