Each sequence fulfills the requirements for physics and biophysics majors (although Physics 161L and 162L are the recommended courses for potential majors), each satisfies the prerequisite physics requirements for majors other than physics and biophysics, and each fulfills the introductory physics requirements for professional and graduate schools.
PHY 161L is only offered in the fall semester and PHY 162L is only offered in the spring.
Th 161L/162L sequence differs from the other introductory sequences (141/142, 151/152/153) in three ways. First 161L and 162L offer a small classroom experience---about 30 students each semester---versus the hundreds of students that take 141/142 and 151/152. The small class allows students and the professor to get to know each other well, which encourage discussion and collaboration, and more creative and interesting labs.
Second, Physics 161L and 162L mention interesting and deeper insights about what is understood about why the laws of nature have the form that they do, or how experiments and theory point to questions that are not yet understood. Physics 161L and 162L will discuss connections of the material to later physics courses, and to various frontiers of science, including research currently being carried out by various professors at Duke.
Third, 161L and 162L differ from the other introductory courses by giving somewhat more derivations of key equations, usually in the context of clarifying why key equations have the form they do, say because of mathematical symmetries or conservation laws.
Note: if you are a freshman thinking of majoring in physics or biophysics and have had some advanced physics in high school (e.g., an AP or IB physics course), it may make sense to skip one or more of the intro physics courses. Please make an appointment with the Physics Director of Undergraduate Studies to discuss this possibility as soon as you arrive on campus. Roughly speaking, if you have a strong background in mechanics but not such a strong background in electrodynamics, you should take Physics 162L. If you have a strong background in both mechanics and electrodynamics (say a score of 5 on both AP Physics C exams), then taking Physics 153L ("Applications of Physics: A Modern Perspective") might be a good choice.
For most freshmen, it is useful to take at least one intro physics course before sophomore year (to gain college-level problem solving skills), and it is important to build up math skills, by taking multivariate calculus (Math 212) no later than the spring semester of their freshman year.
The Physics 141L ("General Physics I: Mechanics") and Physics 142L ("General Physics II: Electricity and Magnetism") sequence is intended for students who are taking calculus for the first time or who are not planning to major in physics or engineering. About three quarters of 141/142 students are interested in the life sciences (for example, biology, psychology, and neurobiology), and many of these students in turn are premeds. The remaining quarter is a mix of students from chemistry, environmental science, mathematics, computer science, and other disciplines.
The 141 and 142 courses differ from the other introductory physics courses primarily by emphasizing examples and applications over derivations. Some instructors do discuss examples related to the life sciences but students should understand that 141L and 142L are physics courses first, with the goal of giving students a broad and useful understanding of the principles and applications of physics. The sequence does cover most physics topics of the MCAT exam, although often in greater detail and with deeper insight than what is required for the MCAT.
For those who want one-on-one tutoring, some free tutoring is available through Duke's Peer Tutoring Program, but this is limited to 12 hours per semester and there is sometimes not enough tutors to satisfy the demand. The Physics Department also keeps a list of tutors. You contact these people directly and the fee is set by the individual tutor.