Automotive
Discussion
Started 17 September 2023
Diffraction caused by an obstacle
The theme of the diffraction typically refers to a small aperture or obstacle. Here I would like to share a video that I took a few days ago that shows diffraction can be produced by the macroscopic items similarly:
I hope you can explain this phenomenon with wave-particle duality or quantum mechanics. However, I can simply interpret it with my own idea of Inhomogeneously refracted space at:
Most recent answer
Dear Researchers,
I am pleased to share my latest work on optics and diffraction, focusing on the deformation of shadows when they intersect. This article has recently been published in the European Journal of Applied Physics. I hope you find it intriguing.
Best regards, Farhad
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Popular replies (1)
Automotive
Finally, I could make new 3D models to do the experiments of shadows comparing the diffraction. Here is the result. I added the new items to the previous video. I hope you like it.
Best regards
Farhad
3 Recommendations
All replies (12)
University of Technology of Troyes
There's no need yo involve diffraction here. What you're seeing is basically a Moire pattern due to the ladder obstructing the lights. It only looks odd because everything is out of focus.
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Automotive
Loïc O. Le Cunff maybe the video is sometimes out of focus but not my own eyes that I could see. By the way, any light that passes by an obstacle gets diffracted. Please study again your modern optics book. After the Fraunhofer diffraction, it is about the obstacle.
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University of Technology of Troyes
1) The diffraction pattern is oscillatory in nature. For monochromatic light, you won't have a sudden dark fringe follow by a sudden bright one. You'll see gradual transitions between both.
2) Those are obviously not monochromatic lights. As such, there is no reason all wavelengths should be extinguished at the same time in dark fringes. One would instead see color variations.
3)Let's do dome rough calculations. In the k-space the diffraction pattern for an aperture or object will be similar to sinc(a*k) where a is the half width of the object.
That means the first 0 will be for k=pi/a.
But that is the tangential component of hhe k vector only, or the sine of its projection.
So, if you want to find the corresponding angle you have
Sin(ang) = pi/a / (k0) = lambda/(2a)
Let's say 2a=3cm and lambda=600nm (yellow), we obtain
sin(ang) = 600e-9 / 3e-2 = 2e-5 ~ang
As such, if you where at 10m from the latter, the corresponding length projected on the sensor of your camera would be roughly
L ~ ang * 10 = 0.2 mm, wich is much smaller than the sensor itself. So we should see the diffraction pattern of it had any actual energy in it.
You did not see diffraction.
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Automotive
Again I suggest you study the different diffraction patterns including Glory and how a small pinhole acts as a low-pass filter for spatial frequencies. With your concerns, these are illustrations as well.
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Dear Farhad Vedad ,
I agree with Loïc O. Le Cunff .
To my opinion this phenomenon is due to Moire effect, as Loic mentioned already.
Please see the attachment...
Modulation (contrast) of diffraction peaks from one or two edges of an obstacle on a high intensity back ground, such as the 'front of the hotel', is too low to be observable here as dark and nearly black spot(s).
A second and striking aspect has been also raised by Loic in his second answer; any diffraction fringe(s) should be coloured, due to the white light of the 'hotel front'...
Best regards
G.M.
Automotive
Gerhard Martens Dear Gerhard, Moire effect is about images, not light sources. The difference is similar to mixing RGB and painting colors.
Appart from Glory and the video of that ladder, I have another video of how diffraction happens by macroscopic items. Please see this one as well:
Kind regards,
Farhad
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Automotive
Gerhard Martens Loïc O. Le Cunff Dear researchers, to complete my recent answer and make it more clear that the shadow experiment is not about penumbra I add more input:
Please watch this 7-8 minutes video at: https://youtu.be/qllMMrgn-mI
To see how the shadows moved out for the item closer to the screen and moved inboard for the item closer to the light source, I attached an image and also I squeezed this image along Y axis to demonstrate this effect exaggerated.
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Automotive
Gerhard Martens Loïc O. Le Cunff Dear researchers, I prepared a better video to explain the shadow effect that is considered similar to the other video of the ladder and the lights of the hotel.
Please see at: https://youtu.be/iT5uoTXeOUo
In the same way, as the shadows move inward or outward, the light of that hotel is declined so the size of the dark band changes.
I hope you like the video. If so, please do not forget to share with other researchers who may interested in this optical thing.
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Automotive
Finally, I could make new 3D models to do the experiments of shadows comparing the diffraction. Here is the result. I added the new items to the previous video. I hope you like it.
Best regards
Farhad
3 Recommendations
Automotive
So, similar to what I showed at
I would say that the light bands (and the dark bands where light is absent) seem stretched when the light from the hotel passes near the horizontal bars of the lather.
Thank you everyone for attention.
Farhad
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Ndevices Ltd
In fact, similar and maybe even more pronounced effect can simply be observed by eye looking through a very narrow gap between two fingers. Bring two fingers very close (few cm) to one eye and look at distant uniform background e.g. sky or screen. By adjusting with the gap one may see some black strip or even a few of them arising. And at first look it may indeed look like diffraction.
However, one immediately realize that while light has almost 1:2 wavelength range so diffraction pattern would be colored and smeared if sourced by white or near white light.
Also, dimensions involved are much larger than needed to observe explicit diffraction.
The alternative explanations is overlaps of semi-shadows. E.g. the edge of the finger better to say multiple ill-defined edges are de-focused by eye when finger is that close and that creates some grey semi-shadow around the edge/edges.
When another finger is brought close enough, the semi-shadows from edges of that finger will overlap creating some non-monotonic stripped patterns. That pattern looks similar to diffraction but in fact all defined by geometric optics ( actual distance, focus distance, aperture size).
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Automotive
Dear Researchers,
I am pleased to share my latest work on optics and diffraction, focusing on the deformation of shadows when they intersect. This article has recently been published in the European Journal of Applied Physics. I hope you find it intriguing.
Best regards, Farhad
3 Recommendations
Similar questions and discussions
The Shadow Blister Effect
The primary challenge in analyzing the shadow blister arises when the transverse distance between the two edges along the X-axis is either large or when the slit width reaches zero and the secondary barrier overlaps the primary barrier, rendering the "Fresnel Integral" valid. In such scenarios, this phenomenon can also be interpreted using traditional ray theory.
As the transverse distance decreases to approximately a millimeter, the validity of the "Fresnel Integral" diminishes. Regrettably, this narrow transverse distance has often been overlooked.
This article explores various scenarios where the transverse distance is either large or less than a millimeter, and where the secondary barrier overlaps the primary barrier.
Notably, complexity arises when the transverse distance is very small. In such conditions, the Fourier transform is valid only if we consider a complex refractive index, indicating an inhomogeneous fractal space with a variable refractive index near the surface of the obstacles. This variable refractive index introduces a time delay in the temporal domain, resulting in a specific dispersion region underlying the diffraction phenomenon.
Refer to:
http://www.ej-physics.org/index.php/ejphysics/article/view/304
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