1 1 /20 2 /20 3 /20 4 /20 5 /20 6 /20 Optional /20 Sum /100 Name Dec. 24, 2003 Wednesday Department SID University Physics Sample Problems for Final Examination School of Intensive Instruction in Sciences and Arts, Nanjing University Physical Constants Electron charge magnitude 191060. 1=eC Dielectric constant of vacuum 12 01085. 8=F/m Permeability of vacuum 7 0104=N/A2 Vacuum speed of light 81000. 3=cm/s Electron rest mass 231Mev/c511. 0kg1011. 9= em Proton rest mass 227938.3MeV/ckg10672. 1= pm Neutron rest mass 227MeV/c6.939kg10675.1= nm Atomic mass unit 227MeV/c5 .931kg10660. 1amu 1=Electron volt (eV) 1eV=191060. 1J Planck constant Js1063. 634=h Boltzmann constant eV/K1062. 8J/K1038. 1523=Bk Bohr radius 259. 00=aAngstroms Select five out of following six problems. 1. (20pts). (a) In Compton scattering, find the maximum increase of the wavelength of the photon. (b) If the wavelength of the scattered photon is the twice of the wavelength of the incident photon, what is the minimum energy of the incident X-ray? 2.(20 pts) (a) Write the time-dependent Schrdinger equation and the stationary (time independent) Schrdinger equation for a particle of mass m moving in the one-dimensional harmonic potential 2 21)(kxxU= 2 (b) The solution for the stationary Schrdinger equation in the one-dimensional harmonic potential is ?)21( +=nEn, )()(222 xHeNxnxnn=, 1=n，2，3， where mk=, ?=, 21!2 =nNnnand )(nHis the Hermite polynomial with the highest power n. We know that )(nHis an even or odd function if nis even or odd. If there is a particle of mass m moving in the potential += , 0, 0,21 )(2xxkxxU find the stationary wave functions and the energy levels of the particle. 3.(20pts) If we put 6 identical bosons or 6 identical spin-1/2 fermions into a one-dimensional infinite well of width a (the energy levels for a particle of mass m in the well is 22222manEn?=). (a) Draw a schematic diagram to show how the energy levels are filled in each case when the system is in the ground state. (b) Find the ground state energy of the system in each case. (c) The atomic mass of a copper atom is 63.55; the density is 8.96 gcm-3. Calculate the Fermi energy FE of the electron gas in copper. (Assume there is 1 valence electron per atom for copper.) 3 4. (20pts) Radioactive nuclei with decay constant are produced in an accelerator at a constant rate pR. (a) Derive the differential equation for the number of radioactive nuclei N (b) If the number of the nuclei is zero at 0=t, find the number N as a function of time t. (c) 62Cu is produced at a rate 100 per second by placing ordinary copper(63Cu) in a beam of high-energy protons and 62Cu decays by beta-decay with a half-life of 10 min. How many 62Cu are there after the time long enough so that 0dtdN? 5.(20pts) The empirical binding energy of a nucleus can be written as ()12 4312 33221=AZNaAZaAaAaEb (the pairing energy is not included), where Z is the atomic number, A is the mass number and N is the neutron number of the nucleus. The values of the constants are MeV.a8151=,MeV.a8172=,MeV.a7103=,MeV.a7234=. (a) Determine the atomic number of the most stable nucleus for a given mass numberA. (b) Explain the physics meaning of the result. 4 6. (20pts) Determine if the following processes are mediated mainly by strong, electromagnetic or weak interactions or forbidden. Explain why. (a) 0+. (b) + (c) e+(d) +0K Optional Problem (20pts) Consider a spinless positive pion decaying at rest. (The initial angular momentum and linear momentum of the pion are zero.) A positive muon and a muon neutrino are emitted in opposite directions with equal and opposite momenta. Meanwhile, the two emitted particles have equal but opposite spins due to the angular momentum conservation. (a) Draw a figure to show the process and the mirror image process of the decay. (b) Can the mirror image process occur in nature? Why? (c) What interaction governs the positive pion decay? (d) What conclusion can you draw if the mirror process can/cannot occur in nature?