German physicist Joseph von Fraunhofer observes and draws dark lines in the solar spectrum

French physicist André Marie Ampère begins his researches into the links between electricity and magnetism

French physicist Augustin Jean Fresnel publishes the theory that light is a transverse wave, thus explaining polarization effects

German physicist Georg Simon Ohm formulates his law about the proportionality of current flowing in an electric conductor

English scientist Michael Faraday reports his discovery of the first law of electrolysis, to be followed a year later by the second

Austrian physicist Christian Doppler explains the acoustic effect now known by his name

Scottish physicist William Thomson, later Lord Kelvin, proposes the 'absolute' scale of temperature

French physicist Léon Foucault demonstrates the rotation of the earth by means of a long pendulum suspended in the Pantheon in Paris

Scottish physicist William Thomson formulates the second law of thermodynamics, concerning the transfer of heat within a closed system

Scottish physicist James Clerk Maxwell presents to the Royal Society his discoveries in the field of electromagnetics, now known collectively as Maxwell's Equations

William Crookes develops a special tube, now known as the Crookes tube, for the study of cathode rays

Scottish physicist William Ramsay isolates argon, following Rayleigh's discovery that an undiscovered gas combines with nitrogen in the air

German physicist Wilhelm Roentgen discovers rays that can penetrate light-proof barriers, and names them x-rays because their nature is as yet unknown

French physicist Antoine Henri Becquerel discovers in uranium salt the phenomenon of natural radioactivity

English physicist Joseph John Thomson, working at the Cavendish laboratory in Cambridge, discovers the existence of the electron

German physicist Max Planck proposes the revolutionary concept of the quantum theory

A.E. Kennelly and Oliver Heaviside independently see the link between the atmosphere and the behaviour of radio waves

Ernest Rutherford and Frederick Soddy identify the phenomenon of radioactive half-life

Albert Einstein explains the photoelectric effect as a flow of discreet particles (quanta) of electromagnetic radiation

In his special theory of relativity Albert Einstein reconciles the apparent clash between relativity and electromagnetic theory

Albert Einstein relates mass and energy in the equation e = mc2

German physicist Walther Nernst establishes the Third Law of Thermodynamics, dealing with temperatures close to absolute zero

German physicist Hans Geiger, working in England with Rutherford, develops an instrument that can detect and count alpha particles

US physicist Robert A. Millikan devises an oil drop experiment that determines the charge of an electron

Charles Wilson, using his cloud chamber to detect the passage of charged particles, obtains his first photographs of alpha and beta rays