PHYSICS LABORATORY 3 (UNIT 2)
Learning outcomes of the course unit
Beyond its specific content concerning the experimental techniques dealt with, the main purpose of this course consists, on one hand, in making students understand the basic concepts of modern physics in their experimental evidence, on the other, in helping developing a correct experimental attitude. The latter involves understanding the operation principles of the equipment; developing criticism towards experimental results, namely, taking into account their range of confidence, minimizing the sources of systematic errors, and recognising the possible effect of instrument malfunctions; evaluating the experimental data properly; 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 with transport measurements, and of the angular energy spectrum of gamma rays in Compton scattering.
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) aimed at giving the essential theoretical and technical-instrumental background to the the understanding of the experiments. 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.