Question

The fission of ${}^{235}U$ can be triggered by the absorption of a slow neutron by a nucleus. Similarly a slow proton can also be used. This statement is

• A. correct
• B. wrong
• C. information is insufficient
• D. none of the above

Answer 1

Answer: (B)

Because the neutron has no electric charge, it experiences no electric repulsion from a $U^{235}$ nucleus. Hence, a slow moving neutron can approach and enter a $U^{235}$ nucleus, thereby providing the excitation needed to trigger fission. By contrast a slow moving proton feels a strong repulsion from a $U^{235}$ nucleus. It never gets close to the nucleus, so it cannot trigger fission.