PHYSICS LABORATORY 3 (UNIT 1)
Learning outcomes of the course unit
Learn the basics of modern Physics.
To get acquainted with the difficulties inherent the planning of a new experiment.
To get some sensitivity in order to evaluate the magnitude of the different variables
that come into play.
Laboratorio di Fisica 1,
Laboratorio di Fisica 2
Course contents summary
The available experiments are:
- Millikan: classic experiment presented in didactic version, allows you to calculate with a certain approximation the value of the elementary electric charge.
- photoelectric effect: classic experiment in didactic version, allows to observe the particle nature of electromagnetic radiation and you to measure Planck's constant, known spectral lines of the mercury source and the value of the elementary charge.
- Thomson: classic experiment in didactic version, to evaluate the relationship and / or m "specific charge" of the electron.
- Franck-Hertz: the classic experiment in didactic version, further automatedto see the quantization of energy levels. This experiment also provides an example of non-conventional spectroscopy.
- visible black body: you will have to measure the intensity of light emitted by a black body temperature of between 800K and 3300K. In a second step, dealing with different experimental difficulties, it will then be possible groped to characterize the spectral curve (Planckian) in the range of wavelengths from visible to near infrared.
- UV-vis absorption spectroscopy: Students become familiar with the spectrophotometer and its limits by verifying the law of Lambert-Beer. Later you can run several experiments on kinetics of evolving physical systems (diffusion of ions in solution, molecular photoisomerization, etc.).
- Fluorescence spectroscopy: we study the fluorescence of a fluorophore in function of its concentration, highlighting the different regimes. It is strongly it recommended that you have already done the experience of the UV-visible absorption spectroscopy.
- Brownian motion: measurement of the thermal agitation of colloidal particles of micrometer size suspended in water (relevant properties to a file in the archive of educational materials) through an optical microscope, digital camera and PC used in Matlab environment. Measured mean square displacement of particles as a function of elapsed time, through the analysis of Einstein, it is possible to derive an estimate of Avogadro's number.
- LCD: students, once familiar with the polarizing optical microscope, the observed birefringence of the behavior of some crystalline and / or polymeric liquid systems, as a function of temperature and applied electric field in a cell that will 'was from them to' built purpose.
- Measurement of viscosity in a transition of gelation. Via a torsion pendulum, machine-readable that students will have to develop and optimize, we will measure the viscosity of some solutions that transiscono to gel.
- Measurement of percolation transition in a granular mixture similar to a fractal: it is a transport measure in a granular medium. Measuring the electrical conductivity (DC or AC, with 2 or 4 points) in a series of pads prepared by mixing a conductive powder (Cu) and an insulator in varying proportions.
Original papers by Millikan, Einstein, Perrin, and some instrument manuals are provided during the course.
Moreover, these are useful texts:
- Horowitz and Hill. The Art of Electronics, Cambridge University Press
- R.A.L. Jones Soft Condensed Matter. Oxford University Press
The course begins with lectures common to all students, to outline the conceptual basis of the experiments available, highlighting the possible experimental difficulties and measures to overcome them.
Then the laboratory sessions follow, where students, in groups of 2 or 3, do 2 or 3 experiments .
Assessment methods and criteria
Oral examination (colloquium) consisting in the discussion of the reports of the experiments performed by each student. This colloquium is typically in February, while a 2.nd colloquium, for the 2.nd modulus, is held typically in the summer session.
The final score for the course is the average of the scores of the two colloquia.
For the analysis of the experimental data it is strongly recommended that students learn to use Matlab efficiently.
For some experiences it is necessary to use a minimum of electronic instrumentation for the acquisition of signals, such as a computer with a data acquisition card (ADC).
Some experiences require digital acquisition and processing of films and images and / or microimages. The Matlab procedures for extracting quantitative information from images are described in a tutorial provided in the archive.
Students are encouraged to keep a "log book" accurate and updated, to write down all observations which may serve to describe or to repeat the experiment. In addition, it is useful that each group will re-encounters in the course of the week discuss and / or seek clarification from the teacher, available on appointment also outside of laboratory time.