LABORATORY FOR MODERN PHYSICS
Learning outcomes of the course unit
Understand basic concepts of modern physics. Become aware of thevarious levels of difficulty involved in conceptualising and designinga new experiment and then take on and solve all problems as they arise.Develop the capacity to evaluate the orders of magnitude of thevariables in play. Develop the critical ability to differentiate basicissues from marginal ones, to evaluate cause and effect, thesuitability of assumptions and approximations adopted, the validity ofthe hypotheses and theoretical models utilised for interpretingresults. Stimulate creativity in approaching an experimental problem inorder to identify new and better solutions and strategies. Applyanalytical skills in order to discover discrepancies and possiblesources of error.
The labs of the first two years, Physics I and II and closecollaboration with the professors of the Quantum Mechanics andIntroduction to Modern Physics courses is recommended to reduce thenumber of hours of classroom lessons, as well as to provide studentswith a unified concept of modern physics. A close working relationshipexists with the Modern Physics II Laboratory to offer the broadest andmost comprehensive perspective possible.
Course contents summary
The experiments available are:
IR black body: In this experiment, the (Planckian) spectral distribution of infrared energy in the area of 400-8000 cm-1is measured, with a temperature source that varies between RT and 1600Kand spectrophometer whose spectral efficiency must be measured.
Visible black body:the Planckian characteristic of a black body at a temperature ofbetween 800K and 3300K must be measured by measuring the spectralemission in a wavelength range of between visible and 1100nm.
Brownian Movement:measurement using optical microscope, camera and frame-grabber of theheat agitation of colloidal particles of micrometric size suspended in water.Once the average squared motion of the particles on the basis of thetime lapsed has been measured using Einstein analysis, an estimate ofthe Avogadro number can be obtained.
UV-Vis absorption spectroscopy:students will become familiar with spectrophotometry and itslimitations through verification of the Lambert-Beer law. Followingthis they will be able to perform a number of kinetic experiments onphysical systems in evolution (ion diffusion in solutions, molecularphotoisomerization, etc.).
Liquid crystals:Once familiar with the polarized light microscope, students willobserve the birefringence behaviour of a number of liquid crystaland/or polymeric systems on the basis of temperature and electricalfield applied in a chamber they have constructed on-site.
Millikan:classic experiment presented in didactic form, to calculate the valueof the elementary electrical charge with a certain approximation.
Photoelectrical effect:classic experiment presented in didactic form to observe thecorpuscular nature of electromagnetic radiation and measure the Planckconstant, note the spectral lines of the mercury source and the valueof the elementary charge.
Thomson: classic experiment presented in didactic form to provide a very rough evaluation of the e/mo specific electron charge.
Franck-Hertz:classic experiment presented in didactic form and further automated bythe teaching lab staff, to highlight the quantization of energy levelsin the atom. This experiment also provides an example ofnon-conventional spectroscopy.
Studentsare encouraged to keep a precise and up-to-date log in which to add allobservations that could be of use in describing or repeating theexperiment. In addition, given that the course meets only once a week,it is recommended that each group meet on its own during the week toreview the situation and/or request ulterior explanation from theprofessor in order to make maximum use of the only afternoon labavailable.
To analyse experimental data, students are strongly encouraged to learnand utilise Matlab and the minimization tools provided, including MINUIT for Matlab (interface created by G. Allodi).
For some work, students must know how to use at lease basic electronic instruments for signal acquisition, such as a computer equipped with a data acquisition card (ADC).
Available for student use are photocopies of parts of a number of books(Eisberg Resnick, "Quantum physics" and Caforio Ferilli "Physica") aswell as a number of original articles by Millikan, Einstein and Perrin,as well as photocopies of manuals for various pieces of equipment.
The course will begin with a number of theoretical lessons for allstudents in which will be presented the conceptual bases of theexperiments available, while also emphasising the historical aspect ofkey experiments that mark the passage from the traditional approach tothat of “modern” physics and references the courses of Quantum Mechanics and Introduction to Modern Physicsfor further information. Following these will be 2x12 lab sessions inwhich students in groups of 2-3 students each will perform 3 or 4experiments. Given the large number of students enrolled, the coursewill be divided into 2 afternoons and each student is required toattend 48 hours of lab work
EVALUATION: The exam consists of the discussion of the reportprepared by students on the experiments they have performed. To beuseful, these reports must be submitted on completion of eachexperiment, not all together at the end of the course.