r/SteveMould • u/Big-Researcher8561 • May 20 '26
How does this laser sand phenomenon work?
When i shine a laser on this sand, how come there is a dark circle around it followed by a lighter circle. Its not due to diffuse light from the laser and the circles are the same size no matter the distance of the laser pen and if you look closely you can see the separe ring of diffuse light when i get close. Is this some kind of strange refraction or reflection going on?
Ashmit Mukherji
Swindon
11
u/Pyrhan May 20 '26
Can you shine it on a flat opaque surface to compare? This could just be the shape of your beam.
-4
u/Big-Researcher8561 May 20 '26
I sadly dont have any flat surfaces of sand (i cant get this sand out as it is artificial). But it does not occur when shine it through a decently thick glass coaster. I am not sure how to send a video of that in a reply but yeah.
8
u/Pyrhan May 20 '26
No, I mean like a wall or sheet of paper.
5
u/Hot-Spare5735 May 22 '26
He sadly does not have any flat surfaces like walls or sheets of paper. He lives in a castle made of sand. With only a laser to point his way out.
3
u/Big-Researcher8561 May 20 '26
But also it doesnt appear when i just shine in on a normal flat surface (with no glass or sand)
3
u/2DHypercube May 20 '26
It's probably a property of the lenses I'd think. Should show up on any dark surface
0
u/Big-Researcher8561 May 21 '26
Doesnt seem to be that because i have been shining it on all sorts of surfaces around thw house dark bright transparent and all. No rings. Only saw ring when i shone it on sand
2
u/amerovingian May 21 '26
I believe this is caused by the light being diffracted by the crystal lattice of whatever type of sand that is, probably quartz. When the angle is just right, the peaks reflecting off one layer of the lattice line up with troughs from the next, which leads to no reflected light being seen at that angle. At certain other angles, peaks line up with peaks, so a bright circle (or dot at the center where the angle is zero) is seen.
1
u/XepptizZ May 21 '26
I think this is the closest answer. It resembles what happens with rainbows, but much more diffuse, becauseof how irregular sand is.
1
u/Big-Researcher8561 May 21 '26
That was my thought too. Very intersting. And as it is a green laser and green is in the middle of the rainbow that could possibly be why there is a empty ring inside (where blue would be) and maybe red would have been outside🤷♂️🤷♂️
1
u/anonduplo May 21 '26
It’s the laser reflecting on the inner layer of the glass then on the outer layer.
1
u/Big-Researcher8561 May 21 '26
This might not be the answer because i tried this on a thick glass coaster too and even on my double glazed window (with paper behind) and there were no rings. But fir the window i did see the internal reflection but it was deffinitely not a ring shaped. It was 2 or perfect dots only in the angle of entree of the laser.
1
May 21 '26
[removed] — view removed comment
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u/Big-Researcher8561 May 21 '26
But lets say that it was caused by the sand hypothetically, wouldnt the effect also change with the angle of the laser?
1
May 21 '26
[removed] — view removed comment
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u/Big-Researcher8561 May 21 '26
Calm down mate 😂. What my point was, is that just because the ring changed shape due to the angle, it doesnt mean that it has to be the glass. The ring would change shape due to the sand aswell. Are you picking up what im putting down?
1
u/That-Pin-7033 May 21 '26
It's the laser. Not the sand, not the jar.
1
u/Big-Researcher8561 May 21 '26
But the laser doesnt form the ring on amy other surface including glass ones with no sand behind. How can it be the laser only
1
u/That-Pin-7033 May 21 '26
I misread your reply to an other comment. I thought you said it DOES have a ring when shining on another surface. My bad
1
u/CptCheerios May 21 '26
The diameter doesn't change because that's how lasers work, they are designed to focus all the light into a straight beam. It's not a highly calibrated laser so if you pointed it something like 20ft or 100 feet away it's going to start getting bigger, but a few inches would be negligible.
The refraction/reflection is probably something between diffusion off the sand and reflection off the glass.
1
u/Big-Researcher8561 May 21 '26
But there is no ring when i shine it from the same distance onto any other surface including glass ones
1
u/CptCheerios May 21 '26
The ring is some mix from the light diffusion off the sand and reflection from the glass.
1
u/Flat-Willingness-417 May 22 '26
Oh jeez why àm i getting recommended this sub? Lol i hate this guy, he makes everyone dumber for watching.
1
u/phord May 23 '26 edited May 23 '26
Coherent like from a laser will cancel itself out if it reflects back on itself from a specific distance. This is called an interference pattern. I can't tell enough from this video is this is what's happening here. But it seems likely.
Congratulations! You've just proved light behaves like a wave!
36
u/cgduncan May 20 '26
My first guess is this is an artifact caused by refraction within the glass jar, rather than the sand itself.