| ~300 BC | Euclid (Alexandria) In his Optica he notes that light travels in straight lines and describes the law of reflection. He believes that vision involves rays going from the eyes to the object seen and studies the relationship between the apparent sizes of objects and the angles that they subtend at the eye |
| Probably between 100 BC and 150 AD | Hero (also known as Heron) of Alexandria. In his Catoptrica, Hero shows by a geometrical method that the actual path taken by a ray of light reflected from a plane mirror is shorter than any other reflected path that might be drawn between the source and point of observation. |
| ~140 AD | Claudius Ptolemy (Alexandria). In a twelfth-century Latin translation from the Arabic that is assigned to Ptolemy, a study of refraction, including atmospheric refraction, is described. It is suggested that the angle of refraction is proportional to the angle of incidence |
| 965-1020 | Ibn-al-Haitham ( also known as Alhazen) (b. Basra). In his investigations, he used spherical and parabolic mirrors and was aware of spherical aberration. He also investigated the magnification produced by lenses and atmospheric refraction. His work was translated into Latin and became accessible to later european scholars |
| ~1220 | Robert Grosseteste (England). Magister scholarum of the University of Oxford and a proponent of the view that theory should be compared with observation, Grosseteste considers that the properties of light have particular significance in natural philosophy and stresses the importance of mathematics and geometry in their study. He believes that colours are related to intensity and that they extend from white to black, white being the purest and lying beyond red with black lying below blue. The rainbow is conjectured to be a consequence of reflection and refraction of sunlight by layers in a 'watery cloud' but the effect of individual droplets is not considered. He adheres to the view, shared by the earlier Greeks, that vision involves emanations from the eye to the object perceived. |
| ~1267 | Roger Bacon (England). A follower of Grosseteste at Oxford, Bacon extends Grosseteste's work on optics. He considers that the speed of light is finite and that it is propagated through a medium in a manner analogous to the propagation of sound. In his Opus Maius, Bacon describes his studies of the magnification of small objects using convex lenses and suggests that they could find application in the correction of defective eyesight. He attributes the phenomenon of the rainbow to the reflection of sunlight from individual raindrops |
| ~1270 | Witelo (Silesia). Completes his Perspectiva which is destined to remain a standard text on optics for several centuries. Amongst other things, Witelo describes a method of machining parabolic mirrors from iron and carries out careful observations on refraction. He recognises that the angle of refraction is not proportional to the angle of incidence but is unaware of total internal reflection |
| 1303 | Bernard of Gordon (France). A Physician, he refers to the use of spectacles as a way of correcting long-sightedness |
| 1304~1310 | Theodoric (Dietrich) of Freiberg. Theodoric explains the rainbow as a consequence of refraction and internal reflection within individual raindrops. He accounts for the appearance of a primary and secondary bow but, following earlier notions, he considers colour to arise from a combination of darkness and brightness in different proportions |
| ~1590 | Zacharius Jensen (Netherlands). Constructs a compound microscope with a converging objective lens and a diverging eye lens. |
| 1604 | Johannes Kepler (Germany). In his book Ad Vitellionem Paralipomena, Kepler suggests that the intensity of light from a point source varies inversely with the square of the distance from the source, that light can be propagated over an unlimited distance and that the speed of propagation is infinite. He explains vision as a consequence of the formation of an image on the retina by the lens in the eye and correctly describes the causes of long-sightedness and short-sightedness |
| 1608 | Hans Lippershey (Netherlands). Constructs a telescope with a converging objective lens and a diverging eye lens. |
| 1609 | Galileo Galilei (Italy).Constructs his own version of Lippershey's telescope and starts to use it for astronomical observations. |
| 1610 | Galileo Galilei (Italy). Using his telescope, Galileo reports several astronomical discoveries including that Jupiter has four moons. |
| 1611 | Johannes Kepler (Germany). In his Dioptrice, Kepler presents an explanation of the principles involved in the convergent/divergent lens microscopes and telescopes. In the same treatise, he suggests that a telescope could be constructed using a converging objective and a converging eye lens and describes a combination of lenses that would later become known as the telephoto lens. He discovers total internal reflection, but is unable to find a satisfactory relationship between the angle of incidence and the angle of refraction |
| ~1618 | Christopher Scheiner. Constructs a telescope of the type suggested by Kepler with converging objective and eye lenses |
| 1621 | Willebrord Snell (Leiden). Discovers the relationship between the angle of incidence and angle of refraction when light passes from one transparent medium to another. |
| 1647 | B Cavalieri. Derives a relationship between the radii of curvature of the surfaces of a thin lens and its focal length |
| 1657 | Pierre de Fermat (France). Enunciates his principle of 'least time', according to which, a ray of light follows the path which takes it to its destination in the shortest time. This principle is consistent with Snell's law of refraction |
| 1663 | James Gregory (England). Suggests the use of a converging mirror for the objective of a telescope as a cure for aberrations |
| 1665 | Francesco Maria Grimaldi (Italy). In a book entitled Physico-Mathesis de lumine, coloribus et iride published posthumously, Grimaldi's observations of diffraction when he passed white light through small apertures are described. Grimaldi concludes that light is a fluid capable of wave-like motion |
| 1665 | Robert Hooke (England). In his treatise, Micrographia, Hooke describes his observations with a compound microscope having a converging objective lens and a converging eye lens. In the same work, he describes his observations of the colours produced in flakes of mica, soap bubbles and films of oil on water. He recognises that the colour produced in mica flakes is related to their thickness but is unable to establish any definite relationship between thickness and colour. Hooke advocates a wave theory for the propagation of light |
| 1666 | Isaac Newton (England). Discovers that white light is splt up into its component colours by passing through a prsim |
| 1668 | Isaac Newton (England). As a solution to the problem of chromatic aberration exhibited by refracting telescopes, Newton constructs the first reflecting telescope |
| 1669 | Erasmus Bartholinus (Denmark). Descovers double refraction in calcite |
| 1672 | Isaac Newton (England). Newton's earlier observations on the dispersion of sunlight as it passes through a prism are reported to the Royal Society. Newton concludes that sunlight is composed of light of different colours which are refracted by glass to different extents |
| 1676 | Olaf Römer (Denmark) Deduces that the speed of light is finite from detailed observations of the eclipses of the moons of Jupiter. From Römer's data, a value of about 2 x 108 m.s-1 is obtainable |
| 1678 | Christiaan Huygens (Netherlands). In a communication to the Academie des Science in Paris, Huygens propounds his wave theory of light (published in his Traite de Lumiere in 1690). He considers that light is transmitted through an all-pervading aether that is made up of small elastic particles, each of which can act as a secondary source of wavelets. On this basis, Huygens can account for many of the known propagation characteristics of light, including the double refraction in calcite discovered by Bartholinus |
| 1704 | Isaac Newton (England). In his Opticks, Newton puts forward his view that light is corpuscular but that the corpuscles are able to excite waves in the aether. His adherence to a corpuscular nature of light is based primarily on the presumption that light travels in straight lines whereas waves can bend into the region of shadow |
| 1727 | James Bradley (England). Bradley calculates the speed of light from observations of the 'aberration' of light from stars, an apparent motion of a star arising from the value of the speed of light in relation to the speed of the earth in its orbit |
| 1733 | Chester More Hall. Constructs an achromatic compound lens using components made from glasses with different refractive indices |
| 1752 | Melvil. Observes that the spectra of flames into which metals or salts have been introduced show bright lines characteristic of what has been introduced into the flame |
| 1801 | Thomas Young (Scotland). Provides support for the wave theory by demonstrating the interference of light |
| 1802 | William Hyde Wollaston (England). Discovers that the spectrum of sunlight is crossed by a number of dark lines |
| 1808 | Etienne Louis Malus (France).As a result of observing light reflected from the windows of the Palais Louxembourg in Paris through a calcite crystal as it is rotated, Malus discovers an effect that later leads to the conclusion that light can be polarized by reflection |
| 1814 | Joseph Fraunhofer (Germany). Fraunhofer rediscovers the dark lines in the solar spectrum noted by Wollaston and determines their position with improved precision |
| 1815 | David Brewster (Scotland). Describes the polarization of light by reflection |
| 1816 | Augustin Jean Fresnel (France). Presents a rigorous treatment of diffraction and interference phenomena showing that they can be explained in terms of a wave theory of light |
| 1816-1817 | As a result of investigations by Fresnel and Dominique Francois Arago on the interference of polarized light and their subsequent interpretation by Thomas Young, it is concluded that light waves are transverse and not , as had been previously thought, longitudinal |
| 1819 | Joseph Fraunhofer (Germany). Describes his investigations of the diffraction of light by gratings which were initially made by winding fine wires around parallel screws |
| 1821 | Augustin Jean Fresnel (France). Presents the laws which enable the intensity and polarization of reflected and refracted light to be calculated |
| 1823 | Joseph Fraunhofer (Germany). Publishes his theory of diffraction |
| 1828 | William Nicol (Scotland). Invents a polarizing prism made from two calcite components. The device becomes known subsequently as a "nicol prism" |
| 1835 | George Airy (England). Calculates the form of the diffraction pattern produced by a circular aperture |
| 1845 | Michael Faraday (England). Describes the rotation of the plane of polarized light that is passed through glass in a magnetic field (the Faraday effect) |
| 1849 | Armand Hypolite Louis Fizeau (France). Using a rotating toothed wheel to break up a light beam into a series of pulses, Fizeau makes the first non-astronomical determination of the speed of light (in air). Obtains a value of 313,300 km.s-1 |
| 1850 | J L Foucault (France). Foucault determines the speed of light in air using a rotating mirror method. Obtains a value of 298,000 km.s-1.In the same year, Foucault uses a rotating mirror method to measure the speed of light in stationary water and finds that it is less than in air |
| 1855 | David Alter (USA). Describes the spectrum of hydrogen and other gases |
| 1859 | H L Fizeau (France). Performs an experiment to determine whether the velocity of light in water is affected by flow of the water. He finds that it is, the change in the velocity of light being about a half the velocity of the flowing water |
| 1861 | Robert Wilhelm Bunsen and Gustav Kirchoff. Perform experiments leading to the conclusion that the dark lines in the solar spectrum observed by Wollaston and Fraunhofer arise due to the absorption of light by gases in the solar atmosphere that are cooler than those emitting the light |
| 1865 | James Clerk Maxwell (Scotland). From his studies of the equations describing electric and magnetic fields, it is found that the speed of an electromagnetic wave should, within experimental error, be the same as the speed of light. Maxwell concludes that light is a form of electromagnetic wave |
| 1869 | John Tyndall (Ireland). Describes experimental studies of the scattering of light from aerosols [Phil. Mag. 37, 384; 38 , 156, 1869] |
| 1871 | John William Strutt, third Baron Rayleigh (England). Presents a general law which relates the intensity of light scattered from small particles to the wavelength of the light when the dimensions of the particles is much less than the wavelength.[Phil.Mag. 41, 107,274,447, 1871] He also makes a 'zone plate' which produces focussing of light by Fresnel diffraction |
| 1873 | Ernst Abbe (Germany). Presents a detailed theory of image formation in the microscope |
| 1874 | Marie Alfred Cornu (France). Describes a graphical approach (the Cornu spiral) to the solution of diffraction problems |
| 1875 | John Kerr (Scotland). Demonstrates the quadratic electro-optic effect (the Kerr effect) in glass |
| 1879 | Josef Stefan (Austria). Presents an empirical relationship which asserts that the total radiant energy emitted from a body per unit time is proportional to the fourth power of the absolute temperature of the body |
| 1879 | Thomas Alvin Edison (USA). Invents the electric light bulb |
| 1882 | Albert Abraham Michelson (USA, b. Germany ). Describes the Michelson interferometer |
| 1885 | Johann Jakob Balmer (Switzerland). Presents an empirical formula describing the position of the emission lines in the visible part of the spectrum of hydrogen |
| 1887 | Albert A Michelson and Edward W Morley (USA). Describe their unsuccessful attemps to detect the motion of the earth with respect to the 'Luminiferous Aether' by investigating whether the speed of light depends upon the direction in which the light beam moves (The Michelson-Morley experiment) |
| 1887 | Heinrich Hertz (Germany). Accidentally discovers the photoelectric effect |
| 1890 | O Wiener. Observes standing waves in light reflected at normal incidence from a silver mirror. Nodes and antinodes in the standing wave are detected photographically and it is concluded that a node exists at the mirror surface. From this it is concluded that, at least as far as photographic effects are concerned, the electric component of the electomagnetic wave has the more important effect |
| 1896 | Wilhelm Wien (Germany). Describes how the spectral distribution of radiation from a black body varies with the temperature of the body [Annalen der Physik 38, 662, 1896] |
| 1896 | Pieter Zeeman (Netherlands). Observes that the spectral lines emitted by an atomic source are broadened when the source is placed in a magnetic field |
| 1899 | Lord Rayleigh (England). Explains the blue colour of the sky and red sunsets as being due to the preferential scattering of blue light by molecules in the earth's atmosphere. [Phil. Mag. 47 , 375, 1899] |
| 1899 | Marie P A C Fabry and Jean B G G A Perot (France). Describe the Fabry-Perot interferometer |
| 1900 | Max Karl Planck (Germany). In his explanation of the characteristics of the radiation emitted from a hot black body, Planck finds it necessary to introduce a universal constant described as the quantum of action, now known as Planck's constant. A consequence is that the energy of an oscillator is the sum of small discrete units, each of which has a value that is proportional to the frequency of oscillation |
| 1905 | Albert Einstein (Germany). Explains the photoelectric effect on the basis that light is quantized, the quanta subsequently becoming known as photons [Annalen der Physik 17, 132, 1905] |
| 1908 | Gustav Mie (Germany). Presents a description of light scattering from particles that are not small compared to the wavelength of light, taking account of particle shape and the difference in refractive index between the particles and the supporting medium |
| 1913 | Neils Henrik David Bohr (Denmark). Bohr advances a theory of the atom in which the electrons are presumed to occupy stable orbits with well-defined energy. The absorption and emission of light by an atom occurs as a result of an electron moving from one orbit to another of different energy. This allowed an explanation of the observation that atoms absorb and emit light at particular frequencies that are characteristic of the atom |
| 1916 | Albert Einstein (Germany). Proposes that the stimulated emission of light is a process that should occur in addition to absorption and spontaneous emission |
| 1926 | A A Michelson (USA). Performs a series of experiments to determine the speed of light using a rotating mirror method with a light path from the observatory at Mount Wilson to a reflector on the summit of Mount San Antonio, a distance of 22 miles. Obtains an average value of 299,796 km.s-1 |
| 1927 | Paul Adrien Maurice Dirac (England). Presents a method of representing the electromagnetic radiation field in quantized form [Proceedings of the Royal Society A, 114, 243, 710, 1927] |
| 1928 | Chandrasekhara Raman (India). Observes weak ineleastic scattering of light from liquids, an effect that comes to be known as raman scattering [Indian J. Phys. 2 ,p387, 1928] |
| 1932 | P Debye and F W Sears and also R Lucas and P Biquard independently observe the diffraction of light by ultrasonic waves |
| 1932 | E H Land (USA). Invents "polaroid" polarizing film |
| 1934 | Frits Zernicke (Netherlands). Describes the phase-contrast microscope |
| 1939 | Walter Geffcken (Germany). Describes the transmission interference filter |
| 1941 | W C Anderson. Measures the speed of light using a Kerr cell to modulate a light beam that passes through a Michelson interferometer. Obtains a value of 299,776 km.s-1 |
| 1948 | Dennis Gabor ( b.Hungary). Describes the principles of wavefront reconstruction, later to become known as holography |
| 1960 | Theodore Maiman (USA). Describes the first laser. The laser was built at the Hughes Research Laboratories and used a rod of synthetic ruby as the lasing medium |
| 1961 | P A Franken, A E Hill, C W Peters and G Weinreich. Demonstrate harmonic generation from light by passing the pulse from a ruby laser through a quartz crystal |
| 1961 | Ali Javan, W Bennett and Donald R Harriott (USA). Describe the first gas laser. Built at the Bell Laboratories, the lasing medium was a mixture of helium and neon and emitted at a wavelength of 1.15 um |
| 1963 | GKN Patel(USA). Announces the development of the first carbon dioxide laser at Bell Laboratories |
| 1964 | William B Bridges(USA). Describes the development of the first argon ion laser at Hughes Research Laboratories |
| 1966 | Sorokin and J R Lankard. Build the first organic dye laser |