Moderator is used in a nuclear to slow down fast neutrons generated after a fission event in the reactor consider a fast neutron (mass `m_(n)`) moving at speed v. The neutron hits a moderator nucleus (Mass M), which is originally static, and gets scattered elastically by `180^(@)`
(a) Find te rato of kinetic energy of the neutron after and before collision.
(b) Show that when `Mgtgtm_(n)`, neutron does not lose much energy and therefore, a moderator should have a small mass number.

Answer

`((M-m_(n))/(M+m_(n)))^(2)`