
8. Consider a quantum particle incident on a one-dimensional abrupt drop potential func- tion V(x) defined as V(x) = -{² 0, if I <0 otherwise (9) -Vo, with the potential drop V₁ > 0 as depicted in the figure below. The particle has mass m and energy E > 0. AV(x) -V (a) Calculate the reflection coefficient for the incident particle from the left as seen in the figure above. Assuming that E = V₁/3, what is the probability that the particle is 'reflected' back? (b) The figure is drawn such that it looks like a car approaching a cliff, but clearly the probability to ‘bounce back’ from the edge of a cliff is far smaller than the probability obtained in (a) unless you are Bugs Bunny! Explain why the potential given by Eq. (9) does not correctly represent a physical cliff. Hint: the potential considered here drops discontinuously from 0 to - V₁ as it passes x = 0, would this be true for a falling car? (c) When a free neutron enters a nucleus, it experiences a sudden drop in potential energy, from V = 0 outside to around -12 MeV inside. Suppose a neutron, emitted with kinetic energy E = 4 MeV by a fission event, strikes a nucleus. What is the probability it will be absorbed, thereby initiating another fission event? Hint: you might find the reflection probability calculated in (a) useful.