Why am I able to see the top of the pictures even though they aren’t facing the reflexive surface. The light would have to travel down through the picture
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5$\begingroup$ If you are talking about the reflected image on the shiny table top, then you are not looking at the top of the photo frames. You are looking at the bottom of the frames reflected in the shiny table top. $\endgroup$– foolishmuseAug 20, 2020 at 20:30
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$\begingroup$ What's more interesting to me is that, in this setup, most of the light reflected off of the glass covering isn't seen in the reflected image - because, while the other stuff is due to diffuse reflection (all directions), the glass is more mirror-like, and the angle is wrong. Didn't think of that before; could be important when painting reflections or doing realistic CGI. $\endgroup$– Filip MilovanovićAug 24, 2020 at 0:12
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6 Answers
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As FGSUZ said, an object doesn't have to face a reflective surface to be seen as an reflection in it. I made the following picture to illustrate it for a 2D illustration:
Two dimensions are sufficient to illustrate it, and it seems to be clearer that way. You can see now that an object doesn't have to face a reflective surface for its image to be reflected from it. The sufficient condition is that the object is visible from a point at the reflective surface.
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The light is bouncing off the top of the picture and hitting a point on the table that then goes to your eye. The image you see in the reflection appears to be under the picture frame but it really isn’t.
I used a pencil to point to where the top corner of the picture frame is being reflected from.
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7$\begingroup$ "The image you see in the reflection appears to be under the picture frame but it really isn’t" The image is indeed directly under the picture frame. The points on the mirror (table surface) which reflect the light going to the camera is what's not under the picture frame. $\endgroup$– PrateekAug 22, 2020 at 14:26
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$\begingroup$ @Prateek: That's a bit of semantics issue. Aaron's way of saying it is not necessarily wrong; e.g., we sometimes say that the image appears to be in some 3D space beyond the surface; which then implies that it's not wrong to say that the actual image is on the surface (i.e., if it was, instead of a mirror, a set of tiny screens/pixels that combine to show the same image, and update based on the camera position, the effect would be practically the same). Of course, the screen analogy breaks down for multiple viewers, so your way of phrasing it may be better if you want to emphasize that. $\endgroup$ Aug 24, 2020 at 0:29
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The confusion comes because you think that something can be seen if it is facing the reflective surface. But that's not true.
Check iamge 1. You think (if I understood right) that the rays from the upper part are "passing hrough the photo" to impact the table...
But that is not what is happening. Check that, if you can see the reflection, that's because the reflection is going to your eyes.
But if you can see the reflection, that's because the rays are going to the palce where the reflection is seen. Check iamge 2:
If the ray were not going there, you wouldn't see the reflection there
You see the reflection because a virtual image is being formed on the table. You see the virtual image on the table. That image is obviously separate from the photo. As long as there is a small angle, it can be seen.
You know, according to Snell's law, the reflected ray will emerge to your eye with the same angle of incidence.
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$\begingroup$ In fact, if you move, the reflection changes as well. It's jsut about Snell's law. Same angle. $\endgroup$– FGSUZAug 21, 2020 at 0:39
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The light coming off the top of the pictures does not have to travel down through the picture, as you say. Take one point on the top of a picture. Because there is a light source beyond the picture, a bundle of rays diverge from that point and strike an area on the table between the picture and you. These rays reflect off of the table, still diverging, and enter you eye. As with a mirror, which the table top is acting as, your eye follows the rays back and they appear to come from a point under the table, forming the (virtual) image of the point on top of the picture.
answered Aug 20, 2020 at 22:02
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some of rays from the top go under an angle to the reflecting table and are reflected to your ey or the camera. if you stand before a mirror of half your size you can still see all of you even your feet, which are not directly across the mirror, but far below.
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Because the reflecting surface is not perfectly smooth. Your picture frames have a "matte" finish. If they were perfectly smooth, you couldn't see the plastic/glass underneath.
