GRE物理Sub题目精选解答.doc

电磁学1. A Fast charged particle passes perpendicularly through a thin glass sheet of index of refraction 1.5. The cone of Cerenkov light, emitted in the glass at angle , is incident on the glass-air interface at the critical angle for total reflection. What is the speed of the particle?answer: 2.answer: D3.answer: E一些简单的量子力学题：1. A particle of charge e and mass m is trapped in a one-dimentional square well of width 2a with impenetrable walls. The walls are located at x=a and x=a.(1)If the quantum mechanical states are labled by n ( n=1 is the ground state), what is the expectation value of x2 for very large n ?answer: a2/3(2) A small electric field of strength E_0 is applied in the x direction. What is the change of the energy of the first excited state of this particle due to this electric field? (Assume that the total potential, due to the walls and the electric field, is 0 at x=0.)answer: 0 2.The wave function where A and b are real constants, is a normalized eigenfunction of the Schrdinger equation for a particle of mass M and energy E in a one dimensional potential V(x) such that V(x)=0 at x=0. Determine the form of the potential V(x)answer: 3.answer: E统计：1.answer: B2.answer: B A一些简单的粒子物理题和狭义相对论1. The half-life of a meson at rest is 2.510 - 8 second. A beam of mesons is generated at a point 15 meters from a detector. Only half of the mesons live to reach the detector. Find the speed of the meson answer: 2.3. A beam of particles is incident on a thin target of thickness t. If the cross section per nucleus for a scattering of the particles by the nuclei of the of the target is , and the number of nuclei per unit volume is n, what is the fraction of particles scattered? answer: nt4.A proton beam is incident on a scatterer 0.1 centimeter thick. The scatterer contains 1020 target nuclei per cubic centimeter. In passing through the scatterer, one