Intersecting Linear Light Strands: A Particle Explanation for the Fresnel Central Spot

23 24 The Fresnel central spot in a shadow, theorized to be generated from wave interference, has given strong 25 support for wave models of light. Using extended exposure macro imaging in various media, the shadow is shown 26 to be more complex with multiple lines of light intersecting in the center. Using the particle concept of discrete light 27 strands perpendicularly reflecting from a diffraction source, these observations can be more accurately explained. 28 Another quantized aspect of light is shown where linear light strands become rings when an energy threshold is 29 reached. 30 31 32 33 34 35 36 37 38 39


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to be more complex with multiple lines of light intersecting in the center. Using the particle concept of discrete light 27 strands perpendicularly reflecting from a diffraction source, these observations can be more accurately explained.

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Another quantized aspect of light is shown where linear light strands become rings when an energy threshold is  Descriptions of light behavior have alternated between particle and wave theory [1,2]. Strong 42 experimental support of both models has led to a dual particle-wave theory. The Fresnel spot, otherwise referred to 43 as the Poisson's spot or Arago's spot, has been utilized to strongly support wave theory [3,4,5]. It is created by 44 projecting light onto a solid disc which then creates a black shadow behind it where light transmission is blocked.

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However, a faint dot of light is visible in the center of the shadow (Figure 1). This is predicted from wave theory 46 wherein new wave fronts, thought to be created at the rim of the disc, interfere with each other as they emanate forward. Constructive interference at the equidistant center of the shadow is thought to create the central spot.

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An alternative particle concept to the wave theory of light has been recently described [6]. Light 49 interference fringe patterns have been shown to be pseudo-interference patterns in certain situations, created by 50 discrete light strands reflecting off a diffraction source. As a substitute to wave interference explanations, the fringe 51 patterns can be explained by these discrete light strands with clear intervening spaces that radiate outward 52 perpendicularly when light hits an edge. Could this alternative explanation apply to the Fresnel central spot? The 53 central spot, its surrounding shadow, and its preceding pathway in free space was analyzed to determine the validity 54 of this conjecture.

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A configuration was assembled to project light onto a solid object creating a shadow ( Figure 2). A 532 nm, 60 5mw spot laser was used as a coherent light source. The light beam was transmitted through a diverging 20D lens.

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The expanded beam was centered over a solid disc which was held with an alligator clamp. The resultant image was 62 isolated using an adjustable iris diaphragm to block higher intensity peripheral light outside of the shadow and allow 63 subtle low light capture. The resulting image was projected onto a black cardstock screen. In another configuration, 64 a solid square object was also utilized to create a shadow. Rings and hollow tubes placed in free space were also 65 used to test the screen image. Images were captured using a Lumix ZS100 digital camera with 20.1 megapixel 1 66 inch sensor and Leica DC Vario-Elmarit Lens F2.8-5.9 using slower shutter speeds for low light extended exposure

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Multiple individual lines of light are viewed radiating towards the center from the rim of the disc shadow ( Figure 3).

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They can be seen intersecting at a central point as they continue past each other. As all lines pass through this 81 central point, it is viewed as the brightest area and appears as a spot from a distance but is irregular when magnified.

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If a ring is placed in front of the lines of light, a sharp corresponding shadow is created that doesn't affect

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This created a solid circular shadow with no light passing through its center ( Figure 5). Light can be seen reflecting 86 off the outer aspect of the tube.

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The alligator clamps, which were holding the disc, blocked light with its two jaws at the rim which is the 88 point of origin of diffraction ( Figure 6). The resulting blockage was distinct with sharp edges that carried to the 89 center of the shadow and conformed to the size and shape of the jaws. If the jaws were moved, the blocked areas 90 moved correspondingly.

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If light was shown on only a portion of the disc rim, then the lines would only occur in that section ( Figure   92 7). If most of the disc rim was left dimmed, except for a small locus, single lines with a fringe pattern would appear.

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A hollow tube placed perpendicularly to the screen, should allow light to pass through if light waves or 136 particles were radiating perpendicularly from the disc. This was not observed, as the shadow was solid when a tube 137 was placed in front of the screen. This observation is more consistent with angled radiating strands being blocked 138 by the perpendicular tube as they try to cross through the center of the shadow (Figure 15, Blockage C).

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Illuminating only a locus on the disc rim only creates lines from that spot. This is consistent with light 140 strands only emanating from that point. These lines also show a fringe pattern. This is consistent with prior

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The periphery of the shadow shows a tendency to form rings (Figure 13). It appears to be dependent upon