Grimaldis analysis of a ray of light assumed to be isolated by a pin hole lead him to propose a conjecture on the nature and propagation of light.
He carefully described the problem of light apparently being deflected when there was no point of incidence and so fraction for the geometric representation of the ray. Neither was their a second point of incidence and so refraction for the exiting ray, and yet the ray was spread, .
He noted the bands of intensity in the image and made a formal analogy with the explanation of a shadow into its umbra and penumbra structure. This slowed him to geometrically introduce the circle of the pinhole as a ring of points of incidence.
Now he could draw rays that emanate from this ring of incidence and pas through into the exiting ray at a slightly deflected angle. He could also intrude the exit circle of the pin hole as a ring of refraction fr some of these deflected rays. On the face of it these considerations should account for the spreading of the ray of light.
However it introduces several problems. Now instead of a single incident ray , multiple incident rays are necessary to account for the point of fraction rotations.. These incident rays must be very close to parallel to achieve the penetration even through a pin hole. Thus a light ray cannot be represented by a single geometric line.
Secondly as the refracted light rays exit the pin hole from the ring of refraction points they must diverge having a complex history of crossings. How can this history be captured by a system of rays, what are the refraction rotations and what about the focus at the points of crossing within the pin hole?
Somehow the faint rings around the bright centre must hold this information. Unlike a penumbra, this was not the absence of light o why were dark rings appearing?
The reigning theoretical conjecture was a pressure in the plenum moving at infinite speed. Grimaldi could not work with that continuum idea, he was an atomistic and a ballistic theorist. Naturally he used a ballistic model. This introduced its own problems. However, it meant that he now represented the incident ray as a collection of incident rays and the exiting ray as a collection of spreading rays which were curiously split. This split he called diffraction. It was not due yo a point of fraction in the line it was due to light being split in nature or split by the collision with the structure of the pin hole.
Eventually Grimaldi had to admit that a wave model based on sound and water models was probably applicable to light also.
Grimaldis mathesis Physico
Some new thinking
We will look at how Newton used Grimali's to support corpuscular optics and how Huygens used it to develop t.he details of the wave (sound and water models) propagation of light.
There is one ther factor that bears on yhis topic, the war between the rationalists who believed god was ultimate and immanent cues, and the empiricists who believed god was a cause only to an otherwise mechanical universe. Thus what was the plenum? Spiritual aether or corpuscular aether, that is spiritist versus atomist, continuum isn't versus discretist. Was the very mature of all things Fractsl?
It seems that Newton was selective in his analysis because he wanted to promote a corpuscular theory of matter in all forms. When he did get the chance he obscured the work of those who held the view that matter was a pi ritual aether. And in that regard he withstood the wave theory of light with all his power.He was against the arrogance of Descartes and his rational superior attitude, and came to disagree with most of Descartes pronouncements based on his rational deductions rather than empirical data.
There is another correction I now
need to make. The diffraction of light was widely observed, but not relative to a camera obscurant pin hole only. In fact it was more commonly observed relative to sharp edges and especially razor sharp edges like knives and razors as used by barbers.,a few others like Hooke and Fabri observed it and associated it with wave behaviours. Couloirs were also observed with rays being deflected into the shadow unexpectedly., and this is hat intrigued Newton into studying optics.
Hooke had a plan to make his name in this area and studied objects using one of the few microscopes available in the world. It was his own design. He examined this behaviour in the wings of moths and butterflies and seeing only sharp ridges he concluded that they were involved in the making of colour by deflecting light as a pressure phenomenon, as was the common scientific belief after Descartes, but that somehow the pressure was transmuted ino the pressure required for the colours. He did not think of it as diffraction or necessarily as a wave.
Newton had not read Grimaldi so he relied on second hand information. As in Chinese whispers he got the wrong impression, believing Grimaldi to be a corpuscularist, and his light rays to be split into corpuscles!. Thus he was intrigued as to how corpuscles could travel to the eye and cause colour. At the time it was believed colour was caused by Descartes pressure impinging the eye, but precisely how was not known Hooke hoped to demonstrate how ridges could deflect this pressure into patterns of colours, and Grimaldis observation seemed to support this idea. In fact Grimaldi conceded to the pressure view as a result of these observations, having been a corpuscularist until then
He named the phenomenon diffraction and meant that a ray of light was mysteriously split into many rays , by a sharp edge. Thus it was natural to define such rays as cut into parts. or diffracted rays. He always meant cut longitudinally, but corpuscularists could not help but think of it cut transversely..
Because there was no surface to be incident on he could not reconcile this splitting behaviour with a ray. In fact he could immediately see that it was modelled by the wave patterns used in the pressure models of sound and water behaviour.
Newton on the other hand, thinking they were cut transversely into little corpuscles or bubbles of light immediately required a ballistic explanation of their continued propagation. He felt that these bubbles would spray out the smaller the aperture, like a fine mist. Ths was a common enough occurrence with an atomiser and with pumped water sprayed onto objects through nozzles. Plus the rainbow was always associated with this kind of restricted flow of liquid.
The experiments with prisms were not just spectacular, they were confirmation of his thinking about corpuscular matter. Thus he was convinced that smaller apertures would split the light more vigorously into a spray and the prism confirmed his notional concept. He called it dispersion, but it relied on light being diffracted transversely. Clearly Newton had created his own meaning for diffraction, and he dropped Gimaldis term and used dispersion instead. Within the dispersed corpuscles of light, because they travelled also in rays, he was able to spot the longitudinal cutting of the rays into bands, these he called inflected , but this was precisely wat Gimaldis defined as diffracted.
Several things now happened that propelled Newton Optiks into the pole position.
His demonstration at the royal society created a spectacular stir, and he was immediately voted into the society. Hooke was incensed at Newtons popularity over his own careful study, and also he saw several errors not the least bing the corpuscular notion of light. .Newton was shakn by this denunciation of his work, and withdrew from society, but his clear nd obvious principles were founded on geometry and one simple axiom light travels in straight lines only. This maintained the geometric ray, his dispersion model supported a refractive index notion for coloured light, and it explained colour as in light mixed in. Implement experiments could be done with light mixing that confirmed expectations and then Newton bought out the reflective telescope based on his optical principles.
The subtleties of light were gone! No one was interested in complex theological and rational arguments for some spiritual aether corpuscles nd atomism was the way to go! Many religious cleric condemned Newton for this one thing, he had trampled over years of inspired rational thinking by the holy ghost and placed in front of the scientific and philosophical mind an empirical method of discovery that denied the trinity!
However many pragmatists and alchemists realised he was using their secret knowledge of matter openly and thus advancing the alchemists cause. All alchemists believed in an atomist view of matter, and when Newton came to his conclusion it was because he was deep into Alchemy, understanding the ancients wisdom about material things. In all his experiments of transmutation he saw nd understood matter as particles or atoms of something could make the most reek able transformations. Pressure had to travel in a plenum. For Newton tht plenum was corpuscular?
Later Newton modified his concept of the plenum to include corpuscles in some kind of Aetheric fluid. But his fluid was entirely material not spiritual.
The Newtonian plenum was therefor a corpuscular fluidic mix, but he had major problems with his fluid dynamical analysis, in book2 so he was still pondering for the rest of his life.
There is a darker side to Newton, which allows me to conjecture that he deliberately promoted the corpuscular theory of light to pave the way for alchemy to become legal in Britain
Now I turn to Huygens, who may ot may nt have read Grimaldie, but Pardies certainly seems to have read the treatise and he helped Huygens to formulate his principle. I produced evidence that Newton had experimental observations on the behaviour of water waves squeezing through a channel. I assume tht this image was well known but mybe not as well drawn, the upshot is that a wavefront propagates as a spherical pressure surface followed bi a spherical low pressure surface. This wave front spreads out relative to a flatish wave front.
Grimaldi initially attempted to explain diffractio by a combination of reflection and refraction. This failed, so he adopted Descartes pressure and the water wave model.
Huygens decided that if rays could spread out then perhaps light propagated in the new way of diffraction all the time. So each point diffracts an incident part of a prior wave front dispersion, by producing its own wavefront dispersion.
A geometrical model would be circles on the circle of a prior circle and so on.. Choosing a specific straight line path from a source would highlight a set of co lineal rays that would ad and subtract to produce the propagation in that direction. The initial pulse would thus be parried to a net zero by a returning expansion. Effects from other point explosions would Cancel out so propagating the pressure pulse in the outward direction.
However if a razor was to block these balancing " forces and pressures" then the pressure would bend away from the straight line ray. That point of incidence would acquire its rotational deflectiondue to sn imbalance in the dispersive ptessures.
Huygens model was difficult to apprehend, and it was a longitudinal pressure propagation. Ultimately it was misapprehended and the simpler ballistic rsy model dominated. In the meantime the sine function crept into the Huygens explanation and seemed to solve several theoretical difficulties, after a fashion.
Fresnel as the story goes was unaware of any of this, but took up a fascination with light. It is difficult to give much credence to the romantic version of the story. Fresnel was deep into the study of light and knew to purchase a diffracter!
Now what such a thing was is unclear, but it was certainly going to be items Grimaldi used in establishing his theory . Thus pin hole cameras, ground lenses that enhanced diffraction and possible early sharp edge slits and grooved materials. Working solely with diffracted light he is said to have made a break through by obscuring a lens with a sharp piece of card. . From this he was able to mathematically adduce new elements into Snells law that accounted for the diffraction patterns, he called this element interference..
Interference is a mathematical model of sine function behaviour. He analysed the refraction of the diffracted fringes or bands of light and found that the combination of the dines in the snell law went to zero. , while in the bright spots the combination went to 2 or more depending on the components included.. This was a secure result that involved treating the diffracted light as a refracted ray. This is significant in the razor edge experiments because there is only, potentially an incident point and so properly the diffracted ray is a deflection or reflection.
Snells laws were examined and enamel refractive indices to be set up. Once set up it was theoretically possible for an incident ray to be refracted internally, and this was experimentally determined. But then this refracted ray, exiting the material could nor " interfere" with light exiting the material from other points and form rainbow patterns to the eye. But this was not diffraction , unless the incident rsy was split apart with a bit being reflected and the remainder refracted. So now diffraction was expanded to mean light split by reflection and refraction at the same surface. This was a twisting of terms. At the one surface a ray could be fractioned but only part go the light was reflected, the other was rotated into the material toward a refraction point.
Without realising it they now had a complex beam of parallel rays being represented by a geometrical line. There was still a single point of incidence but at this point of factorisation the reflection and the refraction rotations could be applied at the same time.
This was where the term polarisation enters the description. It was found that calcite had this property vey markedly. Polarisation of light was defined by this diffractio property., and the fact that images were at right angles to each other and could not be induced to coalesce into one.
Fresnel thus devised the full mathematical description of diffraction as a combination of refraction and reflection.
Arago' realised Fresnel had captured mathematically the known phenomena of light propagation nd immediately revived Huygens wave front theories, now he could use Fresnels interference finding to explain Huygens wave propagation model in terms of interference of the dispersed or diffracted rats at every point..
Poison used the mathematics to disprove the concept and failed by making sn accurate preiction! Suddenly Young whose work had been dismissed was the flavour of the month and progress was rapid in developing the revived wave theory. Fresnel demonstrated mathematically that a longitudinal propagation was not mathematically supported by the equations, but a Transverse oscillation was.
This made no sense unless there was an elastic propagating medium. Fresnel then argued it could not be elastic it had to be rigid. This led to several discussions on e atureandveracity of the aether. In the meantime Faraday, maxwell, Helmholtz, Hertz and Kelvin, we're adding attributes to this aether. It was Faraday and Maxwell he chimed in with the sphere of influence. This was precisely what the Huygens model required to help substantiate it . Huygens complex principle now became a mantra going forward.
Our current theory of light propagation is the Grimaldi- Huygens theory. Both seminal papers have rarely been read. In particular modern experiments throw up questions for those who have developed complex models on the basis of this theory of propagation which is a diffraction theory of propagation.
It should be noted hat Fresnel developed the notion of sine interference before he and Argo calculated the TEM pressure motion, and more importantly before they incorporated polarisation into their model. Consequently the interference of polarised light has to be understood to know precisely what interference patterns on a urface by projection really are. For example does Polarized light scatter in reflection the same way as none polarised or less polarised light? We knw that scattered light from a surface can be polarised by the surface. What if the black light that we do not see is light polarised atl the surface!
We do not realise that sice the discovery of polarised light that all the scattered reflected light we see is to be considered as polarised. It may be that our eyes are tuned to see polarised light and that the sine function interference is a measure of the polarisation of light not the destructive or constructive superposition we are focused on.
I now know that electricity and magnetism have so much more to do with the surface and boundary conditions of moving material in. A dynamic rotating magnetic field. The orthogonality is not just axial, it is phase and also surface orthogonality.