Double Slit Experiment: From Young Till Now

Examining the binding energy inside the atom self field theory (SFT) has discovered that the photon is similar to the hydrogen atom in that instead of being a single particle that acts like a wave it is in fact two-particles acting as two waves. Hence the concepts of quantum entanglement, vector state, etc of the quantum mechanical photon are similar but essentially different to those of SFT. In terms of the double slit experiments, from Young to the modern quantum versions using lasers SFT gives answers compatible with quantum theory. But there is nothing unphysical or enigmatic about SFT, unlike quantum theory explanations of double-slit experiments where unintuitive enigmas are found at every step.

Conclusion: Overall, despite a different mathematical formulation and a different physical picture, there is no  difference between the quantum mechanical solution and the SFT solution for the intensity of the diffraction waveform in the quantum version of the double slit experimentHence there appears to be little further need for the 'many worlds'  or Copenhagen interpretations with their unphysical and metaphysical demands.

*As very well described at genesismission there are other experiments to do with detecting and recording the double slit experiments that will be discussed elsewhere at this site (double slit -shrodinger's cat)

Over the course of the last three hundred and fifty years there have been several completely different ways of understanding light, all accepted by the scientific academies of the day. Although the scientific study of light began long before Newton’s time our modern understanding of light has evolved since the time Newton deduced insights of light’s microscopic nature in the late 17th century.

Figure 1: Newton's prism experiments into light

(Image credit: Molecular Expressions)

Newton saw light as miniscule particles while others including Young viewed light as a wave phenomenon. In the mid-19th century Maxwell supported the wave view via the finding that electromagnetics (EM) was theoretically like sound, where the speed of propagation of the EM wave was in fact the speed of light.

The next major discovery concerning light was by Planck who was investigating the heat generated within a black box. In his mathematical calculations he found that only by allowing the frequency parameter within these equations to be a discrete series of frequency terms did the mathematics make sense numerically. This was pointing towards light being a particle, not just a wave. Einstein took this a step further with his discovery of the photoelectric effect in metals. His experiment confirmed that electrons are confined to the metal, but can escape when provided sufficient photonic energy. Surprisingly when illuminated with infra-red wavelengths (lower energy of around 400 nm or larger) no electrons are emitted from the metal even if the intensity of light is increased. Conversely electron emission occurs at ultra-violet wavelengths (higher energy around 300 nm or smaller) for which the number of electrons emitted now varies with the light intensity. This demonstrated completely the quantized nature of light.

Today, in 2015, it is important to realise that our current understanding of light is based mainly on the requirements and restrictions imposed by quantum theory now almost a century old, i.e. the mathematics of how light is understood. In particular the wave functions of quantum theory are considered part of 'reality'. While the quantum physics results of Planck and Einstein were valid and remain uncontestable, quantum theory was controversial from the start setting in motion a long running debate between Heisenberg, Bohr, and others on the one side, and Planck, Einstein, and others on the other side. This debate still lingers on today although many young theorists are taught quantum theory as if it were now holy writ without learning about the other substantial point of view about quantum theory. It is important to note that some of our current scientific opinions are based on quantum theory which at its heart is incomplete and erroneous. One example of this is its use within the pharmaceutical industry when used to find new drugs; these drugs have side effects associated with them quite possibly because of the erroneous mathematics imbedded within the current mathematical methods used by quantum theory.

Quantum theory emerged at the start of the twentieth century because of the need to describe phenomena that could not be explained using Newtonian mechanics or classical EM theory. A totally new understanding of light grew out of a widespread dissatisfaction with classical EM as stated by Maxwell’s equations as they had evolved at the turn of the 20th century. While EM had been successful at the macroscopic level, physicists found serious problems when they tried to apply the theory to microscopic effects such as the spectra of heated bodies, the spectra of atoms, the photoelectric effect and the problem of the electron as it moved at relativistic speeds. At this point in scientific history many suspected Maxwell’s EM equations while accurate at the macroscopic level were incorrect somehow at the microscopic level.

Up to this stage analysis was performed using Maxwell’s four classical EM equations as the basis of calculations. Bohr used Coulomb’s electrostatic law in his famous early theory of the electron orbiting around the proton in the hydrogen atom that was seen to agree with early spectrographic measurements yet had serious theoretical problems. Without investigating what might have been wrong with classical EM theory itself, i.e. Maxwell’s equations, Heisenberg and Bohr pushed ahead with their new ideas using the same erroneous classical EM theory as the basis of their new quantum formulation. Thus the errors within the old EM theory became imbedded within the new quantum theory. While we can look at this in hindsight the correct theoretical path is clear in retrospect. We will return to this after looking at the history of double-slit experiments; we see only by revising Maxwell’s classical EM equations[1] can we go forward and avoid the awkward Copenhagen interpretation.

At the heart of our current understanding of light is the double slit experiment that Young first used in 1801 to show that light is a wave. The modern double-slit experiment was repeated for quantized light early on in the evolution of quantum theory. There emerged from these experiments the 'many worlds' and  Copenhagen interpretations that were unphysical as well as metaphysical almost demanding the unswerving faith of the practitioner [2]. New ideas based on the revised EM theory and their mathematics lead us to new vistas of scientific understanding about light, physics and life.

Young’s Original Double Slit Experiment


Figure 2: Set-Up for the Young’s original double slit experiment; one tiny pinhole aperture; two tiny pinhole apertures; screen on which the light forms an image See also double slit a video made by MIT's TechTV ( Notice in this MIT video that the double slits (two adjacent slits) are made from the same piece of material, not two different materials, hence the atomic structure of the two slits  is as given in Figure 8 below

Originally Young’s classical wave view of his double slit experiment was used to counter the view proposed by Newton that light acted like miniscule cannon balls. This followed Galileo’s experiments which included dropping cannon balls from the leaning Tower of Pisa.

Newton had empirically determined the gravitational force as a coupling between masses, a mutual interaction similar to SFT. He obtained the inverse square form of the gravitational field first via parabolic calculus. Following Galileo’s experiments, Newton reasoned that if a cannon ball was projected upwards from the surface of the Earth with just the right velocity, it would travel completely around the Earth, and continue to do so forming an orbit. Otherwise it would either return to Earth under gravity in a parabolic flight, or escape the Earth completely and keep flying off spiraling into outer space. The orbital velocity in a particular gravitational field would lead to a period of revolution. He validated his theoretical results using observations of the Moon around the Earth and the planets around the Sun. During his life Newton felt that light too acted like little cannon balls; he used prisms to separate out the wavelengths within white light; the more energy the light had (and therefore the heavier the light) the less it would be bent within the prism.

In Young’s double-slit experiment, light (ideally of a pure colour – that is, a single wavelength – although this is not absolutely necessary) is passed through a narrow slit in a piece of card (‘narrow’ means the slit has to be about as wide as the wavelength of light, roughly a millionth of a metre, so a slit made by a razor is appropriate). Light from these two slits spreads out and falls on a second piece of card in which there are two similar parallel slits. Light from these two slits spreads out in its turn and falls on a screen where it makes a pattern of light and shade, called an ‘interference pattern’. Young explained there is light where the waves arriving from each of the two slits march in step, so that the peaks in both waves add together; there is dark where the waves from the two slits are out of step with each other (out of phase) so the peak in one wave is cancelled by the trough in the other wave. The exact spacing of the pattern seen on the screen depends on the wavelength of the light, which can be calculated by measuring the spacing of the stripes in the pattern. There is absolutely no way to explain this phenomenon by treating light as a stream of tiny cannon balls whizzing through space. (Author's note: This article shows how SFT gives the same solution as quantum theory) Young essentially completed this work by about 1804, and in 1807 he wrote:

 The middle (of the pattern) is always light, and the bright light on each side are at suh distances, that the light coming to them from one of the apertures must have past through a longer spacethan that which comes from the other by an interval which is equal to the breadth of one, two, three, or more of the supposed undulations, while the intervening dark spaces correspond to a difference of half a supposed undulation, of one and a half, of two and a half, or more.

 Ten years later Young refined his model further by suggesting that light waves are produced by a transverse ‘undulation’, moving from side to side, rather than being longitudinal (push-pull) waves like those of sound. Far from convincing his peers, though, Young’s work on light brought him abuse from his physicist colleagues in Britain, angered by the suggestion that anything Newton said could be wrong, who ridiculed the idea that you make darkness by adding two beams of light together.

- Science A History 1543-2001 by John Gribbin, Allen Lane, The Penguin Press, 2002; bold font inserted by the author of this article.

Quantum Version of the Double Slit Experiment

Figure 3: (a) Image in the pinhole camera with a very small aperture; (b) the density of the image along the line AB

Figure 4 (a) The Density of the Image in a two-hole camera according to naïve corpuscular theory is a superposition of images created by the left (L) and right (R) holes; (b) Actual interference picture: In some places the density of the image is higher than L+R (constructive interference); in other places the density is lower then L+R (destructive interference).

Quantum theorists are reared from the cradle on the double slit experiment as illustrated in Figures 1 and 2 below. The figures are based on those in Chapter 3 in the book by Eugene V. Stefanovich’s Relativstic Quantum Dynamics, Mountain View, CA, published in 2004 including the figure captions which are also taken from the text. The experiment has not yet been explained by other than quantum theory as discussed below.

Can the corpuscular theory explain the interference picture? We could assume, for example, that some kind of interaction between light corpuscles is responsible for the interference. However, this must be rejected. For example, in an interference experiment conducted by Taylor in 1909 [2], the intensity was so low that only one photon was present at a time, and any photon-photon interaction was impossible. Another “explanation” that photon somehow splits and passes through both holes and then rejoins again at the point of collision with the photographic plate does not stand criticism as well: One photon never creates two dots on the photographic plate, so it is unlikely that it can split during propagation. Can we assume that the particle passing through the right hole somehow “knows” whether the left hole is open or closed and adjusts its trajectory accordingly? Of course, there is some difference of force acting on the hole near the left hole depending on whether the right hole is open or not. However by all estimates this difference is negligibly small.”

 “The diffraction is rather difficult to reconcile with the corpuscular theory. For example, we can try to save this theory by assuming that the light rays deviate from straight paths due to some interaction with the shield material surrounding the hole.”

It is interesting that Stefanovich twice mentions interaction with the material surrounding the hole because that is precisely the physics that SFT uses to explain the quantum phenomenon without recourse to unphysical mechanisms as in the Copenhagen interpretation.

But before we look at how SFT explains the quantum double-slit experiment, we look at another version of the quantum slit experiment:

 “Young’s double-slit experiment provides the simplest and most fundamental example in which the addition of two coherent waves of light leads to interference oscillations of the light intensity. Photoionization of diatomic molecules represents conceptually a similar phenomenon for the electron waves. Instead of passing through the holes in a screen the photoelectron is ejected from an orbital described as a linear combination of two atomic orbitals localized in different atoms. The interference of the coherent electron waves emitted from two indistinguishable atoms leads to intrinsic interference oscillations similar to YDSE. Cohen and Fano [1] were the first to derive the equation for the total photoionization cross section for the H2 molecule including this YDSE effect. Stimulated by this pioneering work, some theoretical [2–5] and experimental [6–8] studies of ionization of H2 and D2 molecules with different projectiles were performed. Results of these experiments clearly exhibited the Cohen–Fano interference modulation.”

 “Core-level photoemission from molecules like N2 provides a new opportunity to investigate coherent emission of photoelectron waves (see, for example, [9]). For core-level photoionization of these molecules, an additional complication appears due to the presence of the gerade and ungerade 1σ bound orbitals with a very small energy gap between them. This gap is 0.1 eV and is even smaller than the vibrational splitting of ∼0.3 eV. Modern high resolution x-ray photoelectron spectroscopy using synchrotron radiation as a light source is, however, able to resolve this small splitting [10–12]. This opens the possibility of performing YDSE using core-level photoionization of N2 and observing the CF interference modulation.”

We again have quantum theorists close to the true explanation when looking at σ atomic orbitals. As is known somewhat ironically from calculations based on quantum theory σ shells are cylindrically symmetric covalent-like bonds whereas s orbitals are spherically symmetric and associated with hydrogenic structures.

Looking at the quantum mathematics:

Figure 5:  Probability distribution of particle behind double slit, being proportional to the absolute square of the sum of the two complex field strengths.

SFT Version of the Quantum Double Slit Experiment:

As mentioned both σ and s orbitals are symmetric in the axial sense. According to SFT the photon has a hydrogenic composite structure and is illustrated in Figure 4a with an s orbital shape. Further, a multi-atomic structure like a metal has a perfect coherence between atoms; this means all outer shell electrons are synchronous. In addition, there is also an anti-synchronous nature of the electrons that are antisymmetric.  By antisymmetric we mean electrons in filled orbitals such as the σ orbital are at opposite positions within their orbitals; these electrons can be associated with a phase-shift of π radians or 180o. We are now in a position to see clearly how the photon-by-photon build up of a picture of interference occurs within a stochastic process via the individual photoelectric collisions with the sides of each slit without the need for recourse to Copenhagen-like interpretations.

Figure 6 (a) s Orbital of the photon  as given by SFT; σ orbital of the slit material


Figure 7 (a) Multi-atomic slit material composed of regular array of coherent atoms (crystalline); {b) slit shown in material seen as a missing array of atoms.

In the array of atoms that comprises the double slit material all atoms are synchronous (or coherent) in phase; each atom moves in step with all others. Hence when each photon scatters elastically with an atom (leaving aside any vertical effects) there is a relationship between the phase of the outer shell electrons in each atom. As indicated in Figure 8 the outer shell electrons at points a, b, c, and d have related and antisymmetric phases. Atoms at a, b, c, and d corresponding to geometric angles θ=90" and θ'=90" (θ=290" ) as shown in Figure 9 will scatter elastically with a photon somewhat  differently; they are spatially related by the phase of the outer shell electrons. So phase of points a and c are identical and phase at b and d are identical. The surrounding points as shown in Figures 9a and 9b show these neighbouring points can differ from what real numbers might give; remember we are dealing with complex mathematics in SFT where time is concerned (), as in quantum theory.

When we consider all angles of scattering (see Figures 9a and b below) what appears as a stochastic process may result in a photon by photon build up of a deterministic image as in Young's classical experiment (Figure 2).

Figure 8 Double slit shows antisymmetric nature of the (horizontal) sides of both slits . This includes the orbital of the outer shell electrons .

Fresh Look at the Theory of the Double Slit Experiment:

What seems slightly ironic in the historical sense is the fact that SFT gives fresh impetus for a modern reexamination of Newton’s ideas concerning miniscule cannonballs. Of course these cannon balls are actually orbitals related to the photon's and electron's presence and not solid objects. But SFT does see the photon as a particle with mass whereas quantum theory requires a massless photon due to the mathematics.

Figure  9 (a) Photoelectric scatter at angle  radians

Figure  9  (a) Photoelectric scatter at angle radians

 In both the case of the photon and the electron, the motions are bispinorial. In effect this means that each particle is performing two rotations. So the usual ways of determining momentum are changed where two orthogonal forces are involved.

Based on the results of two-slit experiments using electrons, it appears the scattering process described above using elastic photon-electron collisions is able to be replaced by elastic electron-electron collisions with no effect upon the  interference pattern  seen within the results.

Conclusion: Overall, despite a different mathematical formulation and a different physical picture, there is  no  difference between the quantum mechanical solution and the SFT solution for the intensity of the diffraction waveform in the quantum version of the double slit experimentHence there appears to be little further need for the 'many worlds'  or Copenhagen interpretations with their unphysical and metaphysical demands.


[1] In the SFT formulation for the hydrogen atom the fields are spinorial,

, where the form is both relativistic and electromagnetic rather than the electrostatic form of Coulomb’s electrostatic equation and the Biot-Savart equation for magnetostatics. The SFT forms are compatible with the classical electrostatic and magnetostatic forms where the orbital and cyclotron frequencies of a particle are assumed to be ωo=0 and ωc=0. In all cases a finite circulating current is required at  ro≠0 and rc≠0.  Both field forms, the classical and the SFT forms, are identical when a time average is taken for the complex exponential term .

[2] According to Stefanovich in Relativstic Quantum Dynamics,  “In the rest of this book we will try to stay out of this fascinating philosophical debate and follow the fourth approach to quantum mechanics attributed to Feynman: “Shut up and calculate!”