PHYS 4000 Final: PHYS 4000 Final Exam 2007 Fall
Document Summary
The following pages contain text and gures, followed by questions for you to answer. To receive full credit, you must answer the questions clearly and completely; support your answer with a quantitative relation or formula whenever possible. You have until 11:00 am (approximately 120 minutes from now) to complete this exam. A calculator, ruler, and two sheets of formulae (listing any of the. Numbered equations from kittel (or ashcroft & mermin) may be used. The sheet of formulae must be handed in with your answer sheet. Phys 4000 page 2 of 9 (3) [4 points] the phonon dispersion curve along the [111] direction of ge is shown in figure 1. (note: in this gure, q denotes wavevector. ) 1 to estimate the velocity of sound in germanium. Acoustic branches of the phonon dispersion curve for ge. Phys 4000 page 3 of 9 (4) [4 points] fig. Discuss whether it is a better model for acoustic or optical phonons.
