Q1: On an average __________ fast neutrons are produced by nuclear fission of each atom of uranium-235.

ANS:B - 2.5

When uranium-235 undergoes nuclear fission, it splits into two smaller nuclei, called fission fragments, along with releasing several neutrons and a significant amount of energy. The number of neutrons released per fission event can vary depending on the specific reaction and the energy of the incoming neutron (known as the incident neutron). On average, for each fission event of uranium-235, approximately 2.5 neutrons are emitted. This means that, statistically, if you look at a large number of fission events, you'll find that around 2.5 neutrons are released per fission. It's important to note that this number is an average, and in actual fission events, the number of neutrons released can vary slightly above or below this value. These neutrons can then go on to cause further fission reactions in other uranium-235 nuclei, leading to a chain reaction, which is fundamental to the functioning of nuclear reactors and nuclear weapons.