Learning Outcomes and Assessment

The Practical Classes for the IB Physics options (i.e. both the A & B courses) are organized around a set of fourteen experiments, six in the Michaelmas term and eight in the Lent term. Students taking the A, B or both A+B courses undertake different numbers and combinations of these experiments during the year.

Candidates taking a single Physics course will usually undertake a total of either 6 or 7  experiments during the year (3 in the Michaelmas term and either 3 or 4 in the Lent term) attending two 3¾ hour long afternoon sessions (over a fortnight) per experiment. One experiment must be written up as a Head of Class report.  (Students taking only Physics A undertake 7 experiments, whereas students taking only Physics B undertake 6 experiments since they also take an assessed computing course.)

Candidates offering both Physics courses are expected to undertake 6 experiments in the Michaelmas term and 5 experiments in the Lent term, but will complete each of these over the course of a week (usually in one day). They also undertake a longer experimental investigation in groups of four, spread over the practical sessions in weeks 6 and 7 of the Lent term. One of the experiments undertaken in the Michaelmas term must be written up as a Head of Class report.

The primary aim of the classes is to provide students with an opportunity to develop the key skills associated with the design and execution of experiments, and with analysing experimental data, hypothesis testing, presenting results and, importantly (especially for theoreticians), assessing others’ experimental results and analyses. Topics covered include a “systems approach” to experimental design, managing noise, offsets and systematic errors, and using experiments to tie down physical phenomena whose theoretical basis is uncertain or unknown – this is the standard situation for a research physicist. For those taking both the A and B courses, presentational skills and team-working also feature in the extended investigation carried out and assessed at the end of the Lent term.

A secondary aim of the classes is to demonstrate aspects of, and reinforce the content of, some of the Michaelmas and Lent term lectures.

The synopses for both Physics A and B practicals outline the full set of 14 experiments available during the year, although students will only ever be expected to undertake a subset of these. Students must refer to the table at the end of the Lent Term synopsis to determine which experiments they will be required to undertake

Synopsis

LENT TERM: WAVES AND OPTICS – First 5 weeks of term

The first part of the Lent term focuses on investigations that continue the development of the skills associated with the design, execution, and interpretation of experiments. Additionally, they provide further opportunities to demonstrate some of the relevant physical principles developed in the Physics A and B lecture courses.

Students taking only one of Physics A or Physics B will be expected to work in pairs and attend for two afternoon session on the same day on two consecutive weeks per experiment. Pairs will be expected to start these “main” experiments in either week 2, week 4 or week 6 so that at most three from the list below can be undertaken. All single-subject students will also be expected to undertake the short initial class “Key experimental techniques” in week 1 starting at 2pm.

There will be no attendance for single subject students in week 8, and they will not undertake the extended investigation.

Students taking Physics A with Physics B will be expected to work in pairs (or triples – this will depend on the class size) and will undertake each of their “main” experiments in a single weekly session. All double subject students are expected to undertake the initial class “Key experimental techniques” in week 1 starting at their usual 10am or 2pm time.

In weeks 2-5, students will be expected to undertake four experiments chosen from the six main experiments. Note that choice of any particular experiment will depend on space being available, and students arriving first will have the widest selection available. If necessary assignment of experiments will be made to ensure that each student can offer four different experiments.

Students taking Physics A with Physics B will undertake an Extended Investigation, in assigned groups of 4 students, during the practical classes in weeks 6 and 7. In week 8 each group will give a short presentation to the Head of Class , and will hand in the group’s notebook; these will form the basis for assessment.

The experiments offered in the Lent Term are:

[7] Key experimental techniques: Developing observational skills. Basic optical techniques. Using a PicoScope for data acquisition and laptop-based software for data analysis. Random and statistical errors and their diagnosis, practice with Excel.

[8] Fraunhofer diffraction of light: This is investigated experimentally using a laser and a variety of apertures. Quantitative analysis of the measurements is used as a sensitive test of this diffraction theory. The experiment also provides a visualisation of Fourier transforms and helps develop intuition for these and the concept of spatial filtering.

[9] Ultrasonic waves: This experiment is designed to investigate the propagation of ultrasonic waves in air and other fluids. Not only is it possible to examine the standard wave-like behaviour of ultrasound (reflection, diffraction, etc.), but also the experiment demonstrates how ultrasound can be used to probe the kinetic properties of materials.

[10] Waves in liquids: A wave tank is used to study the propagation of waves at the interface layer between two liquids. The dispersive nature of the system makes it particularly interesting. The propagation and spectral structure of wavepackets is also studied.

[11] Fresnel diffraction of light: This experiment demonstrates important features of Fresnel diffraction and allows a quantitative verification of Fresnel theory. It also allows the investigation of off-axis effects which are difficult to analyse theoretically.

[12] Microwaves and waveguides:  A Gunn diode is used to generate microwaves which are used to investigate a wide variety of electromagnetic phenomena using waves with macroscopic wavelength. Propagation is studied in a waveguide and in free space. Interaction with macroscopic objects is studied, including effects of polarisation, reflection, refraction and the production of evanescent waves by total internal reflection.

[13] Interferometers and spectroscopy: Interferometry is a very important tool for spectroscopy and one aim of this experiment is to explore the experimental demands of optical systems in which phase is important. Most experiments use a Michelson interferometer, which provides an introduction to the ideas of Fourier spectroscopy. Some phenomena are also explored using a  Fabry-Perot étalon.

LENT TERM: EXTENDED INVESTIGATION – Weeks 6 and 7; assessment in week 8.

In weeks 6 and 7 of the Lent term students taking both Physics A and Physics B will be expected to undertake a more open-ended and less structured investigation of a single topic over two consecutive weekly sessions. These will be executed in randomly-selected groups of four. The assessment of the investigation will primarily be through a 30-minute long slide-based presentation to a Head of Class in which all the members of the group will be expected to participate. This presentation will take place in week 8 in the same timetable slot as the group’s usual practical class.

[14] Extended investigation: The topic of the investigation may change from year to year.

CHOICE OF EXPERIMENTS in Lent Term

The selection of experiments available for students taking Physics A or B alone and students taking both the Physics A and Physics B courses is summarized in the table below. Experiments marked with a tick (ü) are compulsory. Where a box is greyed-out in a particular column, that experiment is not available for the particular combination of subjects. Experiments from which selection can be made for writing up a Head of Class Report are identified with a report icon (2) .

In all cases, students must attend the first class of the Term on their pre-assigned day of the week at which time the detailed timetable and sequence of experiments will be determined. Students must do all the experiments checked in the relevant column of the table above.

HEAD OF CLASS REPORTING

All students are required to write up one of the experiments they have performed in the form of a formal Head of Class write-up. Students taking only the Physics A or only the Physics B course may choose to submit a Head of Class write-up in either the Michaelmas or Lent Terms. The report must be on one of the experiments marked with the report icon (2) in the table above. Students taking both the Physics A and the Physics B course must submit their Head of Class write-up in the Michaelmas term, again on one of the experiments marked with the report icon in the right-hand column.

Each write-up will be assessed by a Head of Class and the marks awarded will count towards the end-of-year assessment. Students who undertake the extended investigation in the Lent term must also present the results of their investigation in the form of 30-minute-long oral and slide-based presentation to a Head of Class in their final practical session of the Lent Term. As for the Head of Class write-up, this presentation will be assessed by the Head of Class and the marks awarded will count towards the end of year assessment.

Advisory note to candidates taking only the Physics B course:

The practical work in the Michaelmas and Lent Terms draws heavily on lecture material presented in the Physics A course in the Michaelmas Term: students are advised to attend at least the Experimental Methods lectures from the Physics A course for the necessary background to the practical classes.