PHYSICS LABORATORY 3 (UNIT 2)
Learning outcomes of the course unit
The main goals of this course, either specific to the experimental techniques and physics subjects dealt with, or belonging to a broader scope, are detailed as follows. We stress their correspondence to the Dublin Descriptors (DD).
Specific targets are
1) learning the fundamentals of some important experimental techniques (DD: knowledge and understanding);
2) acquiring practical skills about important supporting technologies for experimental Physics (for instance: cryogenics, vacuum techniques, electric signal conditioning);
3) getting a deeper understanding of a few selected topics already treated in introductory courses on Modern Physics, by combining theory with an experimental point of view (DD: applying knowledge and understanding); possibly, extending the body of knowledge available from those courses by means of the student's individual study of supplemental materials provided by the teacher, though under his supervision (DD: learning skills).
Beyond its specific contents, the main purpose of this course may be summarized in helping the student to develop a correct experimental attitude. The latter involves
1) understanding the operation principles of the equipment (DD: knowledge and understanding);
2) gaining self-confidence and autonomy in running experiments;
3) assessing experimental results with criticism (DD: making judgements), namely, taking into account their range of confidence, minimizing the sources of systematic errors, and recognizing the possible effect of instrument malfunctions;
4) evaluating and presenting experimental data with appropriate methods and software tools (DD: applying knowledge and understanding), and presenting experimental results in a concise and direct way (DD: communication skills);
5) following good laboratory practice.
Classical physics; statistical analysis of experimental data.
Course contents summary
After a few classroom lectures, whereby students are provided with the necessary background of physical knowledge and they are shown the operation principles of the employed equipment, students are given the choice of two-three experiments out of five ones available.
The core of the offer is given by magnetic resonances: nuclear magnetic resonance (NMR), with two spectrometers of complementary characteristics, and electron spin resonance (ESR). We stress that the corresponding experimental stations have the character of "big instruments". Students are proposed 1H NMR experiments in liquids, polymers, food, in order to demonstrate the basic concepts of the technique: pulses and transient nuclear response, spin echo, relaxations, motional narrowing in liquids. ESR experiments on free radicals - i.e. DPPH - (either solid or in solution) and on Mn2+ salts involve the hyperfine structure of the resonance line, which may possibly be masked by the dipolar broadening.
Other proposed experiments are the study of superconductive transitions by transport measurements; measuring the temperature-dependent conductivity and Hall ratio in a doped semiconductor; the spectral analysis of electronic noise; the study of the energy of Compton-scattered gamma rays as a function of the scattering angle.
Eisberg Resnick “Quantum physics";
Charles Kittel, "Introduction to solid state physics";
D. Preston, E. Dietz, "The art of experimental physics"
The course is opened by a few introductory lectures (typically 4, two hours each) aimed at giving an overview and the essential theoretical and technical-instrumental background to the the understanding of the experiments. The lectures are supported by the classroom projection of slides, which are made available to students on the Elly platform promptly after their presentation. Any other kind of materials relevant to the specific experiments (teacher's notes, articles and book excerpts, instrument manuals, scientific computer programs) are also uploaded on Elly.
Student groups (2-3 members each) are then led to run a couple of experiments out of a number of proposed ones, each one taking six laboratory sessions (4 hours each) on average. Laboratory sessions are organized into two shifts at a weekly frequency, resulting in a doubled teaching time with respect to the nominal duration of the course. On one hand, the latter is made necessary by the limited number of experimental stations, on the other, it allows the teacher to adequately supervise students in their experimental work, especially at the initial stage. During each experiment, however, students are encouraged to develop increasing autonomy in using the equipment and evaluating the experimental results.
Assessment methods and criteria
Learning verification takes first place in the laboratory sessions, thanks to the continuous presence of the teacher. Students are then supposed to write a report on each experiment, describing in some detail the experiment goal, the available instrumentation, the results obtained. The final examination consists in a colloquium on the experimental reports.
The final classification of students accounts for all the above aspects. In particular, it depends favourably on the following: 1) the commitment, interest and curiosity exhibited by a student while running experiments; 2) the quality of the experimental reports, in particular, the correct treatment of experimental errors, the effective organization of data into appropriate figures and tables, the fit of physical laws to the data; 3) the understanding, on one hand, of the physics involved, on the other, of the operation principles and limits of the laboratory instrumentation, demonstrated by a student in the oral examination.