How IB Physics Is Marked: Papers, IA and Lost Marks

IB Diploma Physics has a new course, first assessed in 2025. The syllabus is organised into five themes, and Paper 1 now includes a section built entirely on data-based questions. If you are revising from older past papers, it is worth being clear about what the current exam actually looks like, and how its markschemes decide which answers earn credit.

The details below come from the IB’s Physics guide for first assessment 2025 and the May 2025 markschemes. Your teacher and the subject guide are the final word for your session.

The course: five themes, SL and HL

The syllabus is organised into five themes: space, time and motion; the particulate nature of matter; wave behaviour; fields; and nuclear and quantum physics. Exam questions regularly cross between them, so a question on a charged particle in a field can just as easily ask for a kinematics calculation or an energy argument.

HL students study everything at SL plus additional higher level material. The IB recommends 150 teaching hours for SL and 240 for HL, and the papers reflect that: they are longer and carry more marks at HL.

How the assessment is weighted

The weighting is the same at SL and HL. External exams make up 80% of the final grade and the internal assessment the other 20%:

• Paper 1 – 36%. SL 1 hour 30 minutes, 45 marks; HL 2 hours, 60 marks.
• Paper 2 – 44%. SL 1 hour 30 minutes, 50 marks; HL 2 hours 30 minutes, 90 marks.
• Internal assessment (the scientific investigation) – 20%, marked out of 24.

A calculator is permitted in both papers, and every student has a clean copy of the Physics data booklet. Some older guides listed SL Paper 2 as 55 marks; the IB corrected this to 50.

Paper 1: 1A and 1B

Paper 1 comes as two separate booklets, completed together in one sitting.

Paper 1A is multiple choice: 25 questions for 25 marks at SL, and 40 questions for 40 marks at HL. No marks are deducted for incorrect answers, so never leave a question blank. The wrong options are written to catch half-learned ideas, so test each option rather than picking the first that looks familiar.

Paper 1B is made up of data-based questions, worth 20 marks at both SL and HL. Expect experimental set-ups, tables of readings and graphs, and questions on reading instruments, uncertainties and whether a result agrees with a reference value. In the May 2025 HL paper, for example, marks went to propagating a fractional uncertainty, quoting a density with its uncertainty, and deciding whether a sample was pure from whether a reference value fell inside that range.

Paper 2: short answers and extended responses

Paper 2 contains short-answer and extended-response questions across the syllabus, worth 50 marks at SL and 90 at HL, with HL papers including the additional higher level material. At 44%, it is the largest single component of the grade, and it is where multi-step calculations and explanations carry the most weight.

The internal assessment

The internal assessment is a scientific investigation: an open-ended task in which you gather and analyse data to answer a research question you have formulated yourself. It is written up as a report of no more than 3,000 words, and the IB recommends around 10 hours of teaching time for it. Data tables, graphs, equations, calculations and references do not count towards the word limit.

It is marked out of 24 against four criteria, each worth 6 marks: research design, data analysis, conclusion and evaluation. Your teacher marks it and the IB moderates the marks. The top band for data analysis asks for clear, precise processing of the data with an appropriate consideration of uncertainties, so plan how you will measure and propagate them before you collect anything. The course also includes the collaborative sciences project, in which students work across science subjects on a shared problem.

How IB physics markschemes work

Every IB physics markscheme opens with the same set of marking notes. Knowing them changes how you write:

• Marks are awarded point by point. Each marking point earns a tick, and notes refer to them as MP1, MP2 and so on. A part marked “max” has more acceptable points than marks.
• A correct answer with no working usually earns full marks, unless the notes say otherwise. But if the working is there and it uses the wrong physics, a correct number is treated as coincidence and penalised. In the May 2025 HL Paper 2, using the Doppler equation for a moving source when the observer was moving scored zero, even though the number came out close.
• Show that means show the steps. The command term show asks for the steps in a calculation or derivation, and calculate asks for the relevant stages in the working. In a show that question the answer is already printed, so the marks are in the steps you write.
• Error carried forward (ECF). If you get an early value wrong and use it correctly later, the later marks are awarded, unless the notes say “Do not allow ECF”. The same principle as method marks at GCSE.
• Units and significant figures are not penalised unless the markscheme notes say so, and some notes do. One May 2025 question accepted only an answer quoted to 3 significant figures, and another required the power of ten to match the unit given. Since you cannot see the notes, always give a unit and a sensible number of significant figures.

Where marks are lost

Most IB physics marks that slip away do so for the same few reasons.

• The wrong equation from the data booklet. The booklet gives you the equations, not the judgement of which one applies. Before substituting, say in a few words which situation you are in (source moving or observer moving, constant acceleration or not).
• Signs and directions. A velocity, a displacement or a field has a direction. In the Doppler question above, a negative answer with no comment earned one mark of two; stating that the observer moved away from the speaker earned both.
• Prefixes and powers of ten. Mixing milligrams and kilograms, or centimetres and metres, is one of the commonest ways to lose a calculation mark. Convert to SI units before you substitute.
• Treating uncertainties as an afterthought. Paper 1B questions expect absolute and fractional uncertainties, quoted to a sensible precision, and a conclusion that uses them. “Repeat the experiment” on its own is not an improvement.
• Missing the command term. State wants a brief answer with no explanation; explain wants reasons or causes; deduce wants a conclusion from the information given. The same thinking applies as with GCSE command words.

How to practise

These habits are learned by writing answers and finding out exactly which marking points they earned. On Exaim, every written answer is marked against the markscheme point by point, so you can see that your method was right but the power of ten slipped, or that you used the right equation in the wrong situation, and fix it on the next attempt.

IB Physics is available at both levels. Start with the free revision notes, flashcards, mind maps and worksheets for IB Physics HL or IB Physics SL, organised by topic and subtopic, or browse every course from the revision resources page.