Fisica II: Elettromagnetismo e Ottica

• This text is a second edition of the book "Physics II, Electromagnetism and Optics" expanded with complements, clarifications, and new exercises.
• It is designed to accompany "Physics I, Mechanics and Thermodynamics."
• Together, the two volumes cover the standard physics curriculum for the first two years of science programs at Italian universities.
• The text emphasizes methodological consistency and the complementary nature of the topics covered in both volumes.

Electromagnetism

• It leverages students' math skills to highlight the predictive power of electromagnetic theory.
• Optics is presented as a consequence of electromagnetism, using its phenomena to validate electromagnetism's predictions.
• This approach diverges from the historical progression of scientific knowledge.
• Numerous examples and exercises are included as integral parts of the text.
• Students are encouraged to use the provided solutions in the appendix only to verify their own work.
• Suggestions at the end of each chapter should only be consulted after serious independent attempts to solve the exercises.

Modern Developments

• The text includes a broad overview of recent advancements in electromagnetism and related technologies.
• Relativistic covariance of the theory is discussed at length.
• A concise but rigorous introduction to quantum mechanics is presented in the last chapter, based on experimental evidence.

Redundancy and Usage

• The text may be longer than the material covered in most second-year physics courses (except physics majors).
• A "reduced path" through the text is marked graphically for other courses.
• This path is identified by small font size and a colored band, indicating less essential material.
• The first edition was tested in various Physics II courses for Physics degrees.
• Improvements were made based on feedback from other science disciplines.
• Acknowledgement is given to colleagues and friends for their support and direction.
• Special thanks are given for the quality and breadth of Ferdinando Amman's and Andrea Frova's suggestions.
• The mathematicians Alessandro Ossicini and Francesco Rosati are acknowledged for reviewing chapters for mathematical accuracy.

Chapter I: Electrostatics in Vacuum - Electric Field and Potential

• Electromagnetic phenomena exhibit a wide variety and complexity in nature.
• From early observations by Thales to the theoretical formulation by Maxwell-Faraday (and later relativistic and quantum extensions by Einstein and Dirac), this field has evolved over 25 centuries.
• Electromagnetism is a major achievement of human intellect, characterized by elegance, synthesis, and predictive power.
• The presentation follows the scientific method, retracing historical steps through schematization.
• It starts with simple situations (static point charges in a vacuum) then gradually introduces complexities (finite dimensions, motion, matter).
• The description presented is the "classical" electromagnetism that historically precedes quantum mechanics and relativity (covered marginally).
• Special relativity is compatible with classical electromagnetism, while quantum mechanics introduces significant changes at atomic scales.

1.1. Electric Actions

• Most forces in macroscopic object interactions are contact forces (friction, pressure, elasticity) or gravitation (weight).
• Simple experiments show that suitably treated macroscopic objects (e.g., rubbed with wool) exert another type of force over a distance i.e., electric actions
• Objects of the same substance, when rubbed, repel each other.
• Objects of different substances, when rubbed, can either attract or repel each other.

Electrification for Rubbing

• Pairs of materials exhibit either repulsive or attractive forces, e.g., glass and plastic, glass and amber.
• Electric forces satisfy Newton's third law (action and reaction).
• Investigation shows that objects separately attracted to a body C after electrification will repel each other.
• If A is attracted to C and B is repelled by C (or vice versa), then A and B will attract each other.
• These conclusions shows the existence of two types of "electrification" i.e. two types of electric charges.
• By convention, glass rubbed with wool gains positive (or vitreous) charge.
• Amber, plastics, or resins rubbed, acquire a negative (or resinous) electric charge.
• Like electric charges repel each other.
• Unlike electric charges attract each other.

Matter and Electric Charge

• Matter in the world (galaxies to molecules) is formed from three fundamental constituents: protons (p), neutrons (n), and electrons (e).
• The mass of a proton (mp) is nearly equal to the mass of a neutron (mn).
• The mass of an electron (me) is about 2000 times smaller than the proton mass: me ≈ mp/1840.
• Protons and neutrons are known as nucleons.
• The diameter of a proton and neutron is about 10^-15 m.
• Electrons are smaller than the precision of current measurements and are therefore considered point-like.
• By convention, protons have positive electric charge and electrons have negative electric charge (equal in magnitude).
• No electric charge has ever been observed as a fraction of proton charge (or electron).
• Elementary charge is the quantized unit of charge i.e. electric charge is quantized.
• Neutrons are electrically neutral i.e., have no electric charge.
• The elemental constituents of matter combine in a variety of ways which are macroscopically visible.
• Combinations are due to two of the fundamental forces of nature.
• Protons and neutrons bind through the nuclear force to form atomic nuclei.
• Nucleus charge is positive, due to the number of protons in it (atomic number).
• Nucleus mass is approximately equal to the sum of the nucleon masses that make it up.
• The number of nucleons making up a nucleus is is its mass number.
• Electrons orbit the nucleus via electric forces, in the number of the atomic number (number of protons), so the overall atom is electrically neutral.
• Atomic neutrality is an example of a general rule better defined from electrostatics.
• Microscopic systems composed of charges yield a global charge equal to the algebraic sum of those constituent charges.

Substances and Electrons

• Atoms of various elements make up all known known substances.
• The number of protons determines which element it is.
• Isotopes are species of the same element which vary in number of neutrons.
• The intensity of electron binding among electrons varies among various substances.
• This particularly applies to peripheral electrons' attraction to a nucleus.
• It follows that there are two key categories of materials: insulators and conductors.

Conduction

• Rubbing two materials can result in electrons passing an electric charge from one to the other.
• Electrons transition from bodies where they have a weaker to stronger nuclear binding.
• e.g., rubbing glass with wool has the effect of removing electrons from the glass.
• The glass will therefore gain a positive charge with an excess of protons.
• Insulators restrain electric charge which has been transferred by rubbing.
• Conductors allow electrons to spread out and prevent electrostatic build-up.

Summaries of Electric Force

• Are a manifestation of nature (attributable to electric charge).
• Obey laws of fundamental interaction among charged particles (i.e., electromagnetic interaction).
• Appear macroscopically when the symmetry of natural electric charge and uncharged matter is broken.
• Electrification can also be transmitted from a charged body to a neutral body by just mechanical contact.
• A charged body can effect a charge a neutral one when in contact (i.e., touching).
• Neutral metals contain free electrons that equalize the concentration of protons.
• Bringing a charged body (e.g. positive insulator) will attract the free electrons in the neutral metal, resulting in concentration.
• If mechanical contact is made, the metalloid electrons will pass to the positive body and depauperate of electrons.
• Depauperation results in positive charge of the initially neutra