LABORATORY FOR ELECTROMAGNETISM AND OPTICS
Learning outcomes of the course unit
The aims of the course are: (i) to give a panorama of simple phenomena of classical electromagnetism, of geometrical optics and wave optics, and (ii) to drive the student towards the acquisition of a correct experimental method and autonomy in the approach to the physical experiments.
The knowledge of the basic concepts of classical electromagnetism and optics is recommended.
Course contents summary
1. Classical electromagnetism
1.1 The magnetic field
Electrical charges moving in magnetic fields: short theoretical recalls. Measurement of the magnetic field intensity: the Hall probe. The Earth’s magnetic field. Experiments: measurement of the magnetic field at the center of a coil and of a couple of Helmholtz coils (and in a solenoid); measurement of the local magnetic field (at the surface of the Earth).
1.2 Electromagnetic induction
The electromagnetic induction, the self-inductance and the mutual inductance: short theoretical recalls. Experiments: determination of the self-inductance of a solenoid and of the mutual inductance of a couple of coaxial solenoids.
1.3 The Hall effect
Resistivity, mobility and carrier concentration in a semiconductor: short theoretical recalls. The ohmic contacts. Experiments: measurement of the resistivity and of the Hall coefficient in a semiconductor at room temperature.
1.4 RLC circuits
Theory of the alternating-current circuits. Series and parallel impedances; complex impedances. Q value of a resonant series RLC circuit. Short accounts on noise and filters. Coaxial cables. Experiments: determination of the resonance frequency and measurement of the width of the resonance peak (Q of the circuit) for a series RLC circuit.
2. Geometrical optics
2.1 Reflection and refraction
Laws of reflection and refraction: short theoretical recalls. Dispersion and prisms. The total reflection. Experiments: measurement of the refraction index of a transparent solid through different methods and comparison of the relative accuracies.
2.2 Mirrors and lenses
Formation of images by reflecting and refracting spherical surfaces. Mirrors and thin lenses. Aberrations. Systems of lenses and mirrors. Experiments: visualization of the image due to a concave mirror; determination of the focal length of a convergent lens and of a divergent lens (through a system of lenses); test of the image magnification law.
2.3 The light
Theory of the electromagnetic waves: short recalls. Generation and polarization of the waves. Coherence. Sources of light: intensity and spectral emission of the main types of lamps. The Laser. The prism spectrometer: dispersive power and resolving power. Experiments: search of the minimum deviation angle for radiations of a fixed wavelength in order to measure the refraction index and to test the Cauchy relation; calibration of a prism spectrometer and identification of an unknown light source by the analysis of its line spectrum.
3. Wave optics
3.1 Interference and diffraction
Interference due to two or several slits and to reflection at thin layers: short theoretical accounts. Fraunhofer diffraction: short theoretical accounts. Short demonstrative experiments. The grating spectrometer: dispersive power and resolving power. Experiments: characterization of a reflection and a transmission grating; acquisition and analysis of a double-slit interference pattern; spectral analysis of a non-monochromatic light source by using a grating spectrometer with or without the insertion of a filter.
Linear polarization of the light: (i) by selective absorption, (ii) by reflection, (iii) by diffusion, (iv) through birefringent plates. Dicroic sheets, birefringent plates. Experiments: test of the Malus law; determination of the Brewster angle for a transparent solid to measure the refraction index; effects due to the presence of half-wave plates and quarter-wave plates.
E.Acerbi, Metodi e strumenti di misura, Città Studi (Torino)
B. K. Jones, Electronics for experimentation and research, Prentice/Hall International (UK) Ltd
R. A. Dunlap, Experimental physics, Oxford University Press
The proposed experiments are introduced through theorical lectures, to recall the basic physical concepts. The experiments are performed by work groups composed by two or three students, who have to operate autonomously under the supervision of the teacher. For each experiment a written relation, containing a critical discussion of the results, is required to the group. The participation of each student to all the experiments is fundamental.
The exam consists in a practical and an oral test. In the practical test the single student has to perform one of the experiments proposed in the course, for choice. The oral test consists in: (i) discussion of the results of the practical test; (ii) discussion on the relations presented by the work group concerning all the experiences performed during the course; (iii) exposition of a chosen topic among those reported in the program of the course.