I had a question about the number of images formed by two mirrors at an angle with each other. This website gives the following picture with 5 total images.

There is a 5th image My question is, what is the basis for the green image? I tried drawing multiple rays from the object to observe how they would bounce and I only seem to ever get two images from one ray because once the second image is produced, the ray leaves the mirror system. This picture, also seems to support my conclusion.

enter image description here

In this instance, the final red ray bounces away from the mirror which means it wouldn't produce the 3rd (the green) image.

  • $\begingroup$ The web page you point to has a (small) image in the upper right with 3 reflections in a 60 degree angle. Is that not what you're looking for? physicsclassroom.com/Class/refln/u13l2f2.gif $\endgroup$ – BowlOfRed Mar 16 '17 at 6:19
  • $\begingroup$ What is the reason you'd use that light ray as opposed to the one I linked in the original post? It seems that depending on the angle of incidence of the first ray it changes whether there are 2 or 3 images. $\endgroup$ – mattzhu Mar 16 '17 at 7:28
  • $\begingroup$ Yes, that's correct. That's why the image only appears in a particular location. Note I5 is in the direction of the vertex from the viewer. $\endgroup$ – BowlOfRed Mar 16 '17 at 7:31

It is not the easiest of diagram to draw.

enter image description here

Image $012$ means that the light came from the object $0$, then reflected off mirror $1$ and then reflected off mirror $2$.

So starting the red ray from object $0$ the reflected ray from mirror $2$ appears to come from image $02$.
In turn that reflected ray from mirror $1$ appears to come from image $021$.
Finally the emergent ray having been reflected from mirror $2$ appears to come from image $0212$.

The blue rays show the reverse sequence of reflections appearing to come from image $0121$.

Update as a result of a further question.

enter image description here

Where back produced the blue and green rays appear to meet is the location of a virtual image.
No image is formed where the rays cross.

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  • $\begingroup$ I have a question ...As in your diagram the blue ray is crossing itself after reflection ..Will it form an image? $\endgroup$ – user35508 Jul 28 '17 at 17:48
  • $\begingroup$ To form an image a number of rays from an object have to meet one another in a region of space.If another blue ray was drawn from the object after two reflections it would emerge diverging from the blue ray that I had drawn. Where those two divergent rays when back produced meet will be the location of a virtual image. I have tried to show that on my second diagram. $\endgroup$ – Farcher Jul 28 '17 at 18:47

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