Physics B

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The Physics B course complements the content in Physics A and is usually the less popular choice between the two physics options available at IB (for those not taking both), particularly because of the greater relevance of the Physics A course’s content to other subjects. It is commonly taken together with Physics A and Mathematics, for those who are certain that will be specialising in Physics or Astrophysics in Part II.   It is also common to take either double physics (A & B) with another unrelated subject or indeed combine single physics (A or B) with other subjects. This would allow one to keep their options open for Part II, but those who are not taking IB Maths would have to attend the Mathematical Methods course in Michaelmas term to build the mathematical background necessary for the concepts that will be covered in Physics B.  Both Physics A & B must be taken at the IB level to take it as a Part II course or as a half subject as part of the Physical Sciences option. Lectures are usually at 9 am on Mondays, Wednesdays, and Fridays.   Physics B begins with Electromagnetism, which builds upon the content briefly covered in the IA Fields course. This course spans 20 lectures, after which comes Classical Dynamics which introduces much more complicated dynamical systems than you might have seen so far (and the tools used to analyse them). This course spans 16 lectures, with the first 4 in Michaelmas. Lastly, the course concludes with Thermodynamics, which introduces you to the analytical and statistical treatment of thermodynamics over 8 lectures before exams begin.   In general, most lecture notes tend to be filled (without blanks for you to fill in), either in the form of slides or handouts, but each course is lectured differently with each lecturer referring to the lecture notes to differing extents. A summary of each lecture course is as follows:   Michaelmas:
  • Electromagnetism: The 20-lecture course begins where IA ended by looking at Maxwell’s Equations, before delving deeper into electrostatics and magnetism. For each case, the course uses vector calculus to derive the relevant Maxwell’s equations and looks at interesting problem-solving techniques such as the method of images. Much of the mathematics covered here provides a neat background when it is covered more rigorously in IB Mathematics. The lecture course itself is rather enjoyable with lots of demonstrations spaced throughout the course, which certainly makes taking the trip down to lecture theatre for a 9 am worth it.
  • Classical Mechanics: This course begins with a brief recap of IA dynamics before rushing into rotating frames. The lecture notes tend to be extremely brief, and this topic takes a few readings to understand. The course then moves onto planetary orbits, before covering lagrangian mechanics, normal modes, elasticity and finally some fluid dynamics. The notes are formatted as slides, and thus read more like revision notes than lecture notes. This means that there is a lot of information that much of which is important, packed into a very short document. There are 4 lectures in Michaelmas and 16 in Lent.
  • Classical Mechanics: (As explained above)
  • Thermodynamics: The final lecture course in Physics B consists of 8 lectures in Lent and 8 lectures in Easter. It is quite possibly the first time you might encounter thermodynamics if you hadn’t taken IA Chemistry and the course is structured with the assumption that you didn’t. Beginning with analytical thermodynamics, you are first introduced to state variables and the laws of thermodynamics, before moving on to phase transitions, and then finally statistical thermodynamics. It is worth highlighting that this course is lectured right before the start of exams, and it is probably a good idea to spend some time in summer looking through the thermodynamics course material to do your future self a favour. As with Classical Mechanics, the lecture notes are slides which makes understanding the material at first glance challenging. A good reference textbook is Concepts in Thermal Physics by Blundell & Blundell. The textbook is easy to understand and entertaining to read (as entertaining as Physics textbooks can get), and can be a lifesaver during the frenzy of Easter term.
  Easter (Thermodynamics):
  • Thermodynamics: (As explained above)


The content covered in supervisions will vary from supervisor to supervisor, but in general, you can expect supervision problems to take longer to solve than they have in IA. Problems are usually graded from A to C, with A indicating a simple problem meant to test basic understanding, and C implying the problem is significantly challenging (similar to Phys A). Most tripos questions would probably fall somewhere between B and C. There are usually one or two computational problems on the example sheet to extend your understanding, which can be solved using content covered in IA Scientific Computing.


As in the case for many Part IB subjects, there is a practical session every week. This can either be a continuous 7h 45min slot (with a break for lunch) on one day, or two shorter sessions distributed over two days depending on your slot allocation. You have some ability to choose your practical slot: It is likely that during the induction briefing at the start of the year you will be handed a piece of paper on the way in. This is randomised and will decide your practical slot, but you can make mutual swaps with others before handing this piece of paper back with your name on it. After this point, it is extremely difficult to change your practical slot.   Practicals are like IA in that marking is formative with standard credit, but there is a graded scientific report due shortly after Michaelmas term ends (or you can instead choose to submit one after Lent term ends if you are taking single physics – refer to the lab manual for more detail). Practicals in Michaelmas don’t necessarily follow the Physics B content very closely, but you are likely to see more Physics B relevant experiments in Lent (for instance there was a practical about Waveguides).   Lent term gets much busier. If you are taking double physics, you will be assigned to a group at the start of Lent and you will be expected to work together on: a scientific poster on a topic in the course syllabus that you will present at a poster session at the end of the term. an extended investigation at the end of the term that will involve using the techniques learnt throughout the Lent practicals to investigate an open problem (e.g., what is the wavelength of a given laser). You then prepare a group presentation detailing your findings. This is also due at the end of the term. If you are taking Physics B as a single physics option, you don’t have to do the extended investigation, or the poster session. Practicals in Lent follow the same format as in Michaelmas vis-à-vis standard credit, but you can choose 3 out of about 5 available practicals to perform in weeks 3, 4 and 5 if you are doing double physics. If you are doing single physics, the choice of practicals has some restrictions which are detailed in the lab handout. Choosing your practical is done at the start of the practical session on a first-come-first-served basis where the limiting factor is the number of setups available for that experiment. It has been the case at least this year that the extended investigation was related to optics, if this remains the case next year, doing the optics experiments would probably provide the most benefit for those doing the extended investigation.

Revision and Exams

In addition to the assessed practical coursework (which forms 25% of the overall grade), there are two 3-hour papers at the end of the year. There is no choice of question, but the content is usually split such that Paper 1 usually covers calculation questions from Electromagnetism and Classical Dynamics, with maybe Section A questions from Thermodynamics, while Paper 2 covers mainly Thermodynamics calculation questions with essay questions related to Electromagnetism and Classical Dynamics. There are 5 short questions in Section A, 2 to 3 long questions and either essay or brief notes questions forming the remainder of the marks.   Past papers are the main resource for revision. The TIS has papers ranging back until 1995 so there is no shortage of these. As for suggested answers, the TIS has these for certain years, though some supervisors provide unofficial solutions for other years as well. The brief notes and essay questions can be prepared for by preparing essay plans. There is a somewhat limited set of essay/brief notes questions that can be asked; hence it is possible to work through a few years’ worth of questions and find that you have covered a decent chunk of examinable content that can be tested in the form of essay questions.

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