# subtopics

## Optics

Optics is the branch of physics which involves the behaviour and properties of light , including its interactions with matter and the construction of instruments that use or detect it. [ 1 ] Optics usually describes the behaviour of visible , ultraviolet , and infrared light. Because light is an electromagnetic wave , other forms of electromagnetic radiation such as X-rays , microwaves , and radio waves exhibit similar properties. [ 1 ] Most optical phenomena can be accounted for using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice. Practical optics is usually done using simplified models. The most common of these, geometric optics , treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces.

## Maxwell's equations

Maxwell's equations are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics , classical optics , and electric circuits . These fields in turn underlie modern electrical and communications technologies. Maxwell's equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents . They are named after the Scottish physicist and mathematician James Clerk Maxwell who published an early form of those equations between 1861 and 1862. The equations have two major variants.
Magnetic leads here. For other uses of magnetic, see Magnetic (disambiguation) Magnetism is a class of physical phenomena that includes forces exerted by magnets on other magnets.

## Magnetism

Lightning is one of the most dramatic effects of electricity. Electricity is the set of physical phenomena associated with the presence and flow of electric charge . Electricity gives a wide variety of well-known effects, such as lightning , static electricity , electromagnetic induction and the flow of electrical current . In addition, electricity permits the creation and reception of electromagnetic radiation such as radio waves .

## Classical electromagnetism

Classical electromagnetism (or classical electrodynamics ) is a branch of theoretical physics that studies consequences of the electromagnetic forces between electric charges and currents . It provides an excellent description of electromagnetic phenomena whenever the relevant length scales and field strengths are large enough that quantum mechanical effects are negligible (see quantum electrodynamics ). Fundamental physical aspects of classical electrodynamics are presented e.g. by Feynman, Leighton and Sands, [ 1 ] Panofsky and Phillips, [ 2 ] and Jackson. [ 3 ] The theory of electromagnetism was developed over the course of the 19th century, most prominently by James Clerk Maxwell . For a detailed historical account, consult Pauli, [ 4 ] Whittaker, [ 5 ] and Pais. [ 6 ] See also History of optics , History of electromagnetism and Maxwell's equations . [ edit ] Lorentz force

## Electrostatics

Paper shavings attracted by a charged CD Electrostatics is the branch of physics that deals with the phenomena and properties of stationary or slow-moving (without acceleration) electric charges . Since classical antiquity , it has been known that some materials such as amber attract lightweight particles after rubbing . The Greek word for amber, ήλεκτρον electron , was the source of the word 'electricity'. Electrostatic phenomena arise from the forces that electric charges exert on each other. Such forces are described by Coulomb's law .