# Virtual images in (plane) mirrors?

The following image is taken from teaching physics lecture Was man aus virtuellen Bildern lernen kann (in German):

Now the cited paper claims that the left hand side is the correct picture to explain the virtual image if you look with your eyes, the right hand side is correct if you use a camera (but incorrect if the camera is replaced with the eye). In the case of a plane mirror both constructions lead to the same result. However in the case of curved mirrors they lead to different results (which is also discussed in the cited paper). Now I am a bit confused since the right picture (with an eye instead of the camera) is that one typically drawn in physics textbooks (for example Pedrotti "Introduction to optics" p.38 or Halliday Resnick "Fundamentals of Physics" p.1140). So my question is, which picture is the correct one? Do you know further references of papers or books which discuss this problem more in detail? (I have only found this cited paper in German).

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Hello student, I cannot read the interpretations You give in the linked pdf. Do You speak German? – Georg Apr 12 '11 at 19:57
See page 5 below. Yes I am from Germany. – student Apr 12 '11 at 20:14
Ok, I read everything in the text re that pictures, but not the captiones :=( – Georg Apr 12 '11 at 20:14
see also univie.ac.at/pluslucis/FBW0/FBW2008/Material/… p.1 and p.2 from the same author and didaktik.physik.fu-berlin.de/~nordmei/Physik_Grundschule/… p. 3 – student Apr 12 '11 at 20:16
I am really not able to get the difference between the two images. Can you tell if its any particular aspect about which you are talking – bubble Jun 27 '11 at 6:00

Both drawings are correct for both the eye and the camera, as optically the eye behaves like a camera. The difference is that the first drawing shows the principal rays while the second shows the marginal rays.

The marginal rays are interesting mostly when discussing focus and depth of field. Compared to most cameras, the eye has a very large depth of field, and a very good autofocus system. Then, the issues of focus and depth of field are less important for the eye than for the camera. That's why the right picture is just slightly less relevant for the eye.

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I strongly believe that both the images are right. Even the eyes have got lens and you can replace the whole eye with a lens and retina. It is only the way they are representing the information. The first picture is a bit deceptive, in the sense that it hides the basic principle of a point getting focused by a lens on a sensor plane.

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The point of the cited paper is, that the image we see in our mind is in many cases (for example the hollow mirror) not the same as that one you get, if you construct it in the usual way (as in the second picture) because our brain seems to use different informations in different situations to determine the locus of the image... – student Jun 27 '11 at 19:27

I think it isw possible that one is a cocave lens and the other is a convex lens that is also why in the right picture the angles converge

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