# GENERAL PHYSICS

## Learning outcomes of the course unit

This course aims to give to the students the basic knowledge on electromagnetism, general properties of waves, in particular mechanical and electromagnetic waives and principles of geometric and wave optics.

## Course contents summary

1 Electromagnetism

1.1 Current and resistance. Resistance and Ohm law –The Drude’s model – Semiconductors – Parallel and series resistances – Voltmeters and Amperometers

1.2 DC circuits. Batteries – Electric energy – Kirchhoff laws – RC circuit.

1.3 Magnetostatic. History – Magnetic field - Oersted, Ampère, Biot e Savart experiments- Lorentz force – Force on a current - Ampère law – Ampère law applications: linear wire, coil, planar current – Mass spectrometer – Force between currents – Field generated by a coil – Dipolar field – Particles motion in a magnetic field -

1.4 Magnetic induction. Faraday-Lenz law – induced efm – Motors and generators – Transformers and inductances – Reciprocal induction coefficient – Self induction – Magnetic energy.

1.5 Alternated currents. RL circuit – Oscillations in a LC circuit - RLC circuit.

1.6 Maxwell equations. Displacement current - Maxwell equations – Oscillating circuit and the antenna - Electromagnetic radiation - Poynting vector- Radiation pressure and intensity.

2. Waves

2.1 General properties of wave motion

Wave characteristics. Longitudinal and transverse waves. Wave Fronts. Wave function. General wave equation. Phase. Phase velocity. Sinusoidal waves.

2.2 Superposition of waves

The principle of superposition. The Fourier theorem. Interference of sinusoidal waves. Standing waves. Beats. Propagation in dispersive media: group velocity.

2.3 Propagation of mechanical transverse and longitudinal waves

The speed of a transverse wave in a tight string. Equation of the transverse wave. Energy flow and wave intensity for a transverse wave. Reflection and refraction of transverse waves in a string. Transverse standing waves in a string. The speed of a longitudinal wave in the ideal gas. Propagation of acoustic waves.

2.4 Electromagnetic waves

Mathematical derivation of electromagnetic wave equation from the Maxwell’s equations. Plane electromagnetic wave. Polarized waves: linear, circular and elliptical polarization. Spectrum of the electromagnetic waves.

2.5 Energy and momentum of electromagnetic waves

The Poynting vector. Intensity of an electromagnetic wave. Momentum of an electromagnetic wave and radiation pressure.

2.6 Sources of electromagnetic waves

Radiation from an oscillating electric dipole. Short account of radiation from accelerated charges.

2.7 Propagation of electromagnetic waves in matter

Refraction index. Propagation of electromagnetic waves in dispersive media: (1) dielectrics and (2) system of free charges.

3. Optics

3.1 The light

Double nature of the light. Huygens’s principle. Introduction to the concept of ray. Fermat’s principle.

3.2 Wave geometry: plane surfaces

Reflection and refraction of electromagnetic waves at plane surfaces. Derivation of the reflection and the refraction laws from the Huygens’s principle. Dispersion and prisms. The total reflection.

3.3 Wave geometry: spherical surfaces

Reflection and refraction at spherical surfaces. Lenses. Optical systems: the microscope and the telescope.

3.4 Polarization

Methods to obtain linearly polarized waves: (i) selective absorption (dichroism), (ii) reflection at the Brewster angle, (iii) diffusion.

3.5 Interference

Coherence. Interference of waves produced by two synchronous sources. Interference of several synchronous sources. Interference due to a thin layer. Michelson interferometer.

3.6 Diffraction

Fraunhofer diffraction by a rectangular aperture. Resolving power. Fraunhofer diffraction by two equal parallel slits. Diffraction grating.

## Recommended readings

W.E. Gettys, F.J. Keller, M.J. Skove, Fisica classica e moderna 2. McGraw-Hill Libri Italia, Milano, 1998

## Teaching methods

Theoretical lessons will be completed with practical ones consisting into the assisted solution of exercises on the treated arguments. Some demonstration activities (especially on optics) are planned.

## Assessment methods and criteria

The students who constantly attend the lessons and get a pass on the infra annum tests, can take a simplified final exam. The others will have to take a complete one which consists of a written and, if required, an oral test.