This book is intended as a gene ml introduction to modem physics for science and engineering students. It is written at a level which presumes a prior TUII year's с ourse in с lassie al physic s, and a kno wledge of eleme ntary diffe re ntial and integral с aleukiа The ma terial disc usse d here includes probab ility, re lativity, quantum me -с hanic s, a to mic physic s, statistic al me с hanic s, nuc le ar physic s and elementary particles. Some of these tOplCS, such as statistical mechanics and probability, are ordinarily not included in textbooks at this level. However, we have felt that for proper understanding of many topics in modem physic s — suc h as CjUQIltuiTI me-с hanic s and its applic atio ns — this ma te rial is e sse ntial. It is о ur Opinion tha t pre se nt-day sc ie nc e and e ngine e ring stud ents should be ab le to WOTK quantitatively with the concepts of modem physics. Therefore, we have attempted to present these ideas in a manner which is logical and fairly rigorous. A number of topics, especially in quantum mechanics, are presented in greater depth than is customary. In many cases, unique ways of presentation are given which greatly simplify the discussion of there topics. However, few of the developments require mo re ma the ma tic s than ele me ntary с ale ulus and the algebra of complex numbers; in a few places, familiarity with partial differentiation will be necessary. Unifying с о nc e p ts whic h ha lve imp о rtant a pplic atio ns thro ughout modem physics, such as relativity, probability and the laws of conservation, have been stre sse d . Aim о st all the о re tic a 1 de velo pments are linke d to exa mple s and da ta taken from experiment. Summaries are included at the end of each chapter, as well as problems with wide variations in d iffic ulty. This book was written for use in a one-semester course at the SOphomore or | U ПIО Г le ve 1 The с о urse с о uld b e sho rte ne d by о mitting some topics; for example, Chapter 7, Chapter 12, Chapters 13 through 15, and Chapter 16 contain blocks о f ma te rial whic h are so me wha t ind ependent of each о the r. The syste m of units primarily use d thro ug ho ut is the me ter-kilo gra m-se с о nd system. A table of factors for conversion to other useful units is given in Appendix 4. Atomic mass units are defined with the С atom as the standard. We are grateful for the helpful comments of a large number of students, who use d the book in pre liminary ТОГГП fо г a numb er of years. We also thank our colleagues and reviewers for their constructive criticism. Finally, we wish to e x-pre ss о ur thanks to Mrs. Euth Wifeo n fo r he г с are ful typing о f the manusc rip t.