Light through the ages Ancient Greece to Maxwell

Rays and waves : a study in seventeenth century optics, Ph.D. Thesis, Yale Univ.(New Haven, Conn., 1970).,10] for details. Brewsters publication in 1811 gave what is now known as Brewsters law, namely that the maximum polarisation of a beam of light occurs when it strikes the surface of a transparent medium so that the refracted ray makes an angle of 90 with the reflected ray.

thcentury most opinion sided withNewton. He had been right on so many things that it was generally assumed that he must be right about light being corpuscular. Not everyone in the 18thcentury agreed, however, and whenEulerpublished his work on opticsNova theoria lucis et colorumin 1746 it argued strongly for a wave theory of light. Diffraction was the hardest phenomenon to explain with a corpuscular theory, andEulerused it to support his wave theory. He argued strongly for an analogy between light and sound and consequently for the aether which carried light waves as air carries sound waves. The sun, saidEuler, is a bell ringing out light.Eulers theory was in fact the second version of his wave theory of light and details of both theories are considered in [, J Hendry, The development of attitudes to the wave-particle duality of light and quantum theory, 1900-1920,Ann. of Sci.37(1) (1980), 59-79. ,24].

Not everyone believed that sight was explained by a beam coming from the eye. Lucretius wrote inOn the nature of the Universe(55 BC):-

La Dioptriquepublished as a supplement toDiscours de la mthod pour bien conduire sa raison et chercher la vrit dans les sciences.DescartesandFermatcarried on a discussion after this publication (see [, W Tobin, Toothed wheels and rotating mirrors : Parisian astronomy and mid-nineteenth century experimental measurements of the speed of light,Vistas Astronom.36(3) (1993), 253-294.,47] for details) andFermatinitially assumed that they had reached a different law since they had started from different assumptions.Fermatproposed that light follows the path which takes the shortest time, enablingSnells law of refraction to be deduced mathematically. Other contributions around this time byDescarteswas his belief in the mathematical argument byKeplerwhich showed that the image formed on the retina of the eye should be upside-down. He conducted an experiment with the eye of a dead ox, scraping away the retina and seeing that indeed the image was upside-down. Some ofDescartesclaims were fallacious such as his belief that the velocity of light is infinite. He stated, rather foolishly, that he staked his philosophy on that fact. See [, L Rozenfeld, Gravitational effects of light (Russian), inEinstein collection, 1980-1981Nauka (Moscow, 1985), 255-266; 335.,38] for details of whyDescarteswas so strongly convinced.

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Philosophical Transactions of the Royal Societyand in it he gave experimental evidence that light is composed of minute particles. A few years earlier another member of the Royal Society,Robert Hooke, had published a wave theory of light and his own theory of colours. He reacted toNewtons paper by claiming that what was original in the paper was wrong and what was correct in the paper was stolen from him. In [, N Kipnis,History of the principle of interference of light(Basel, 1991).,3] Nakajima discusses theNewtonHookecontroversy of 1672:-

… remains for all time one of the greatest triumphs of human intellectual endeavor.References(49 books/articles)

Optica Promota(1663) he described the first practical reflecting telescope now called the Gregorian telescope. In factGregorymade a fundamental discovery about light a few years later while in St Andrews. He discovered diffraction by letting light pass through a feather but he was not the first to investigate this phenomenon as Grimaldi had studied it a few years earlier. Here isGregorys description:-

The middle of the pattern is always light, and the bright stripes on each side are at such distances that the light coming to them from one of the apertures must have passed through a longer space than that which comes from the other by an interval which is equal to the breadth of one, two, three, or more of the supposed wavelengths, while the intervening dark spaces correspond to a difference of half a supposed wavelength, of one and a half, of two and a half, or more.This description is absolutely correct but it was difficult for people to accept. There is something very definitely counterintuitive in claiming that two rays of light could, under certain conditions, add to give darkness. We should note that Young made other notable discoveries about light, in particular he realised that colour vision was due to the eye having receptors each of which was sensitive to one of the three colours red, green, or blue.

Opticain about 300 BC in which he studied the properties of light which he postulated travelled in straight lines. He described the laws of reflection and studied them mathematically. He did question sight being the result of a beam from the eye, for he asks how if one closes ones eyes, then opens them at night one sees the stars immediately. Of course if the beam from the eye travels infinitely fast this is not a problem. In about 60 ADHeronmade the interesting observation that when light is reflected by a mirror it travels along the path of least length.Ptolemy, about 80 years afterHeron, studied light in his astronomical work. Through accurate measurements of positions of stars, he realised that light is refracted by the atmosphere.

The view which I am so bold to put forth considers radiation as a high species of vibration in the lines of force which are known to connect particles, and also masses of matter together. It endeavours to dismiss the aether but not the vibrations.

thcentury.Keplerworked on optics, and came up with the first correct mathematical theory of the camera obscura. He also gave the first correct explanation of how the human eye works, with an upside-down image formed on the retina. He correctly explained shortsight and longsight. He gave the important result that the intensity of light observed from a source varies inversely with the square of the distance of the observer from the source. He was wrong, however, in arguing that the velocity of light is infinite. He published his results were published inSupplements to Witelo,on the optical part of astronomy (1604). In fact an important discovery had been made earlier byThomas Harriotwhen he discovered the sine law of refraction of light in 1601, but he did not publish the result.

Newton to Einstein(Cambridge, 1992).,1]:-

One of your commissioners, MPoisson, had deduced from the integrals reported by[Fresnel]the singular result that the centre of the shadow of an opaque circular screen must, when the rays penetrate there at incidences which are only a little more oblique, be just as illuminated as if the screen did not exist. The consequence has been submitted to the test of direct experiment, and observation has perfectly confirmed the calculation.thcentury.

It has not been sufficiently emphasized that there existed two kinds of modification theory of colours,Aristotles modification theory and theDescartesHookemodification theory. This seems to have caused some confusion in the interpretation of the optical controversy betweenNewtonandHookein1672. [We]present a new interpretation of the optical controversy of1672.

thcentury. However, without making major advances on the Greeks, some Europeans did make some improvements.Grosseteste, in about 1220, stressed the significance of the properties of light to natural philosophy and in turn advocated using geometry to study light. He put forward theories of colour, however, which have little merit.Roger Bacon, about 50 years later, continued to follow his teacherGrossetestein believing in the importance of the study of light and he did come up with some correct conclusions deduced from experiments carried out in a very scientific way. He believed that the velocity of light is finite, studied convex lenses and advocated their use to correct defective eyesight. About the same time atRoger Baconwas working on optics in England, Witelo was studying mirrors and refraction of light and wrote up his findings inPerspectivawhich was a standard text on optics for several centuries.

Dioptricewhich was another important work on optics. It described how one could put lenses together to give what today is called a telephoto lens. It also described total internal reflection but failed to give the correct law of refraction of light,Harriots result being unknown toKepler(or anyone else) although the two had corresponded.

Treatise on lightuntil 1690. LikeNewton, an interest in telescopes had promptedHuygensto try to understand the nature of light. He proposed a wave theory, but of course a wave has to travel through a medium soHuygensmodel included an all pervading aether which carries the wave. This is similar to the way that sound waves travel. Sound waves travel in air and if a bell is placed in a vacuum then nothing is heard. Similarly, it was believed, light waves needed the aether through which to travel. It was a beautifully worked out theory and explained most of the observed phenomena of light such as reflection, refraction, diffraction etc.

Light in the quantum eraMainindexBiographiesIndexJOC/EFR August 2002

Beguelin compared the Newtonian emission theory of light and the wave theory of LeonhardEuler. Whereas others opted for one of the two theories by invoking arguments or authorities, Beguelin made a systematic search for experiments which he hoped would settle the dispute. Two of these experiments were most original. The first, which Beguelin himself performed, concerned light rays grazing a glass surface. For several reasons it did not have the impact it deserved. The second one was a thought experiment which was meant to illustrate a major tenet of the wave theory, that is, the analogy between light and sound. … neither of them brought the debate to an end.Newton to Einstein(Cambridge, 1992).,1]:-

Let in the suns rays by a small hole to a darkened house, and at the hole place a feather(the more delicate and white the better for this purpose), and it shall direct to a white wall or paper opposite to it a number of small circles and ovals(if I mistake them not)whereof one is somewhat white(to wit, the middle which is opposite the sun)and all the rest severally coloured. I would gladly hear MrNewtons thoughts of it.thcentury, a period where major theories on light would be put forward. These resulted from the contributions ofHuygensHookeandNewtonand two opposing theories were supported. In the 1660sGassendihad put forward the particle theory, suggesting that light was composed of a stream of tiny particles, whileDescartessuggested that space was filled with plenum which transmitted pressure from a light source onto the eye. The wave theory byHuygensandHookewas a development ofDescartesideas where now they proposed that light be a wave through the plenum, whileNewtonsupported the theory that light rays were composed of tiny particles. Let us first examineNewtons major contribution.

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The light and heat of the sun; these are composed of minute atoms which, when they are shoved off, lose no time in shooting right across the interspace of air in the direction imparted by the shove.Despite this remarkably accurate view, Lucretiuss views were not generally accepted and sight was still seen as emanating from the eye.

Acadmie des Sciencesproposed as their prize topic for the 1819 Grand Prix a mathematical theory to explain diffraction.Fresnelwrote a paper giving the mathematical basis for his wave theory of light and in 1819 the committee, withAragoas chairman, and includingPoissonBiotandLaplacemet to consider his work.

Let parallel light impinge on an opaque disk, the surrounding being perfectly transparent. The disk casts a shadow – of course – but the very centre of the shadow will be bright. Succinctly, there is no darkness anywhere along the central perpendicular behind an opaque disk(except immediately behind the disk).Acadmie des Sciences, R Baierlein,Newton to Einstein(Cambridge, 1992).,1]:-

Einstein in context(Cambridge, 1993), 83-106.,22] Hakfoort studies the work of Nicolas Bguelin of 1772:-

Opticksin 1704. These are examined carefully in [, A E Shapiro, Light, pressure, and rectilinear propagation : Descartes celestial optics and Newtons hydrostatics,Studies in Hist. and Philos. Sci.5(1974), 239-296.,41].

Article by:J J OConnorandE F Robertson

This velocity is so nearly that of light that it seems we have strong reason to conclude that light itself(including radiant heat and other radiations)is an electromagnetic disturbance in the form of waves propagated through the electromagnetic field according to electromagnetic laws.Electricity and Magnetism(1873).Planck, who made one of the next major breakthoughts described inLight through the ages: Relativity and quantum era, said on the occasion of the centenary ofMaxwells birth in 1931, that this theory:-

Version for printingThe study of light has been a major topic in the study of mathematics and physics from ancient Greek times up to the present day. This study has on occasion been highly mathematical in nature while at other times it has more relevance to other scientific disciplines. In this article we take a broad look at the topic, although we will emphasis its more mathematical aspects.

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We can scarcely avoid the inference that light consists in the traverse undulations of the same medium which is the cause of electric and magnetic phenomena.Newton to Einstein(Cambridge, 1992).,1]):-

Dark lines in the spectrum of light had first been observed in 1802 by William Wollaston but the correct explanation of them had to wait a few years until a more thorough investigation by Joseph von Fraunhofer who measured the exact positions of over 500 such lines.

Opticksof 1704 andEulers optical work. Perhaps the most significant was James Bradleys calculation of the velocity of light in 1727. This was still an astronomical method, but Bradley used observations of the aberration of light from stars. This is the apparent slight change in the positions of stars caused by the yearly motion of the Earth. It is worth noting that Bradleys work provided first direct evidence that the Earth revolves around the sun.

Opticksin 1704. It discussed the theory of light and colour and dealt with investigations of the colours of thin sheets,Newtons rings, and the diffraction of light. To explain some of his observationsNewtonhad to argue that the corpuscles of light created waves in the aether. However, the work strongly argued for a corpuscular theory of light, with the most telling argument being that light travels in straight lines yet waves are seen to bend into a region of shadow. There was a possible way to distinguish betweenNewtons corpuscular theory andHuygenswave theory. In the former theory it was necessary for light to travel faster in a more dense medium, while in the latter theory light needed to travel more slowly.


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