Strange Optical Phenomenon (mirror in shower)

Discussion in 'Physics & Math' started by Neddy Bate, Oct 19, 2021.

  1. Neddy Bate Valued Senior Member

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    I noticed this strange optical phenomenon when using a mirror in the shower, and I can't figure out the physics of what is going on. If anyone can explain this satisfactorily, I will be very impressed.

    To see this strange optical phenomenon yourself, all you should need is a small mirror and a bathroom shower. There is also a light in the ceiling of the shower, which is probably an LED, but I think this should work in any shower. The effect is especially noticeable for me, because I have dark brown eyes, but I think it should be also be noticeable with any color eyes.

    I made a few sketches so you can see exactly what to look for.

    1. The sketch below is what I see when I look at myself with the mirror held in front of the shower stream:

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    2. The sketch below is what I would expect to see when I look at myself with the mirror held behind the shower stream:

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    3. The sketch below is what I actually see when I look at myself with the mirror held behind the shower stream:

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    Notice how the pupils in the eyes are fully dark, as if they are hovering in front of the shower stream instead of behind it. This effect surely must be related to the fact that the pupils are where the light is entering my eyes to create the image that I am seeing. But what exactly is going on here? It seems like the image of the shower water is being cancelled out by its own reflection, but only where the pupils are for some reason?

    Please explain, thank you.
     
    Last edited: Oct 19, 2021
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  3. Neddy Bate Valued Senior Member

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    Update:
    I tried to replicate this in a different shower with different lighting. The lighting was so different that the shower stream seemed fully transparent, so the phenomenon was not apparent. I brought another light in, and tried some different lighting angles, and I was eventually able to replicate the effect. Apparently the lighting angle has to be such that the shower stream and reflection can both be seen clearly. If the shower stream appears transparent, it will not happen.
     
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  5. DaveC426913 Valued Senior Member

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    Well, I'll throw myself on this grenade and be the first to say it:

    Why you not take your jewelry off in the shower? Also: are you single?
     
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  7. Neddy Bate Valued Senior Member

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    LOL, but I really want to understand the optical physics of this. (Besides me seeing my beautiful self, lol)
     
  8. DaveC426913 Valued Senior Member

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    Indeed, but not much to be said until I replicate the experiment myself.
     
  9. DaveC426913 Valued Senior Member

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    In the meantime, I offer the following experiment to determine if it is an objective phenom or a subjective phenom:

    Cut a piece of flat black material (maybe use a match carbonize a little disc of tinfoil?), and bring it in the shower with you. Hold it up as near to your pupil as you can. See if you get the same effect.

    See, the effect could be simply that your pupil is a very black object (in that it reflects no light at all) - and that the high contrast is what you are seeing. There really aren't very many things in our normal vision that are as high contrast as a black pupil. It may just be blowing right through the weak diffusion of light made by the water stream.
     
  10. Neddy Bate Valued Senior Member

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    Indeed, I would like for you to replicate it! Then you can tell me what you think is going on. Make sure the lighting lets you see both the shower stream and the reflection.
     
  11. Neddy Bate Valued Senior Member

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    No, it does not happen for other dark objects. My eyes are almost as dark as my pupils, (look at the sketch, it is a cartoon, but it there is practically zero contrast between the pupils and the irises.) The shower stream is readily seen in front of my very dark irises, but not at the pupil, which clearly appears to me as an increase in contrast right there. That is exactly what makes it look so strange. (see the sketches)

    It is definitely only the pupil, (you will see when you see it yourself).

    Besides that, the thing you need to explain is why the shower stream cannot be seen in front of the pupil. Just being a dark object does not make the shower stream, which is in front, invisible. But it appears so at the pupil.
     
    Last edited: Oct 19, 2021
  12. billvon Valued Senior Member

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    There are a few related phenomena, but there's nothing that would cause that specific effect.

    One warning I will give you - your eyes don't work like cameras. If there's a difference in contrast around your pupils (for example) you won't see your pupils the same way you see other things. There are a million examples of such illusions out there on the Internet.
     
  13. Neddy Bate Valued Senior Member

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    I think this is more like the red-eye artifact in photography, which also occurs at the pupils. In that sense, the eye is doing something similar to a camera, while also being a biological eyeball with a pupil.

    But somehow it also seems to be like noise-cancelling headphones. Something about the light is cancelling out. I know the shower stream is in front of the reflection, and therefore should be visible. But it doesn't appear to be there (at the pupils), which is like a cross between an illusion and something else. That is why I posted this, it is fascinating when you see it.
     
    Last edited: Oct 19, 2021
  14. Neddy Bate Valued Senior Member

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    In the mirror image, there is also a reflection of the shower stream. So the pupils appear black against both shower stream images (actual & reflected). Not sure if that matters.
     
    Last edited: Oct 19, 2021
  15. exchemist Valued Senior Member

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    Could it be that the shower stream is reflecting additional light onto your face, making everything appear lighter, including the iris of the eye? That might explain why you have to be able to see the shower stream, i.e. it has to be reflecting light, for the effect to appear.
     
  16. billvon Valued Senior Member

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    That's the reflection from your retina itself when the light source (flash) is the same as, or very close to, the lens. In this case, if you had a light source behind the shower, the shower would block the red-eye effect as well.
    That is unlikely.
    I suspect with a good camera it would be visible. Again, your eye is great at creating illusions.
     
  17. DaveC426913 Valued Senior Member

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    OK well, I did the experiment myself and this is what I saw:

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    Sorry. Maybe it's just a brown-eye thing.
     
  18. Neddy Bate Valued Senior Member

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    It is not as simple as everything being brighter. I can move my head slightly to the left or right and watch the effect disappear as soon as my pupil appears to the left or right of the shower stream. Then the effect is still there for the other pupil which still appears behind the shower stream, but only for that one. So the shower stream has to be visible, and it must appear to be in front of the pupil.
     
    Last edited: Oct 19, 2021
  19. Neddy Bate Valued Senior Member

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    Well the shower should be blocking my pupils, with or without any red eye effect. But it does not seem to be blocking it at all, which is the strange thing. The pupils alone almost seem to hover in front of the stream, (which I know is not actually possible).

    Of course in this case it is not a red-pupil-effect, but a black-pupil-effect. There is no red.

    I know, but something is making it look that way.

    I can see the shower stream quite clearly everyplace except the little circle where my pupil is (and only when it is behind the stream). So I know the shower stream is quite visible.
     
    Last edited: Oct 19, 2021
  20. Neddy Bate Valued Senior Member

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    Ha. I do wish someone could replicate this, so that they can see that this is a real thing. I will have someone over this weekend, so I will ask them if they see it happening with their pupil. I don't think anyone can see it happening to any one else, it has to be your own eye. Likewise, a camera could not capture it happening to anyone's eye, but the effect could show up in a photo as a black circle in front of the camera lens, probably something like this:

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    But I have my doubts that the camera would do the same thing as an eye.
     
    Last edited: Oct 19, 2021
  21. DaveC426913 Valued Senior Member

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    I still think you should do the experiment I proposed in post 6.

    You're too close to the issue - you're drawing tentative conclusions about under what conditions you think it is happening, even though you don't know how or why.

    The scientifically responsible thing is to do everything you can to disprove your hypothesis. If those experiments fail to disprove, your hypothesis gets stronger.

    (If you want to test if a beam is strong enough, you don't start at the strongest point - you start at the weakest point and work your way to the strongest. If it fails at the weakest, you don't need to do any more testing.)
     
  22. Neddy Bate Valued Senior Member

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    When my eye appears to the left or right of the shower stream, there is practically zero contrast between my pupil and my dark brown iris. When my eye appears in the shower stream, the contrast between iris and pupil becomes extremely noticeable. This is not something that happens to all dark objects, it is only the pupils. Refer to the sketches to see that the other dark things are not affected the way the pupils are.

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    But I will test your idea next chance I get (I'm not there now...)
     
    Last edited: Oct 19, 2021
  23. Neddy Bate Valued Senior Member

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    This is what it looks like if I move slightly to the side:

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    There is no mistaking the effect, it is clear to see. I am sure no other dark or black object would do this, it is definitely something to do with it being the pupil of the eye that is taking the image.
     
    Last edited: Oct 19, 2021

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