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When an obstacle is put in the path of a liquid jet, some standing waves are created upstream of the obstacle (see the pic. this great picture is taken by a Persian student, Seyyed Ali Madani. his one of my friends and he let me to use this) enter image description here

or we can say a similar form like this for them ( the wavelength of standing waves are much larger than the from below ) enter image description here This way, if the contact point is illuminated by a laser beam, around the waves, we'll have rings of light.

I tried to justify this with internal reflections inside the water jet, but you know, it's very hard to draw it. can anybody help me with that? What's the reason of these light rings

I don't want the reason of standing waves, I want the reason of light rings

David 2000
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  • by rings of light do you mean that the air-water-surface interface is illuminated? – Bruce Lee Jan 05 '16 at 19:37
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    Possible duplicate of Patterns in laminar flow of tap water – Muze Jan 05 '16 at 19:39
  • I thought you meant this https://en.wikipedia.org/wiki/Shock_diamond :D – endolith Jan 05 '16 at 19:40
  • Yes I mean that – David 2000 Jan 05 '16 at 19:40
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    Are these 'light rings' shown in the photograph above? I see something more like dots - which I assume are just reflections of the illuminating source. Can you maybe superimpose arrows on the photo to point at what you are describing in words? – docscience Jan 05 '16 at 19:52
  • Could you clarify "contact point is illuminated by a laser beam" - do you mean the point where the stream hits the obstacle? And further - where and how are "rings of light" observed? Are you holding a piece of white card next to the jet, and do you see circles? Do you see lines (which would be "a circle of light" if you wrapped paper all around the jet)? – Floris Jan 05 '16 at 20:33

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