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I understand how a magnifying glass works as a convex lens, however I am curious as to how one can explain using it as a mirror.

When I observe the reflections off of a magnifying glass, strangely enough it seems to create two reflections: one that is inverted and one that is upright. How is this so? Shouldn't a magnifying glass simply act as a convex mirror, just as it acts as a convex lens? Which images are real, and which ones are virtual images?

I've attached an image I took as an example. In the image, the same house is reflected twice--one is inverted, one is upright.

uncreative
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  • You see two images because one is reflected by the surface of the lens that is facing you, and one is reflected by the farthest surface. As an example, think that, when you are underwater and look up, you see a reflection on the surface. – snefs May 15 '16 at 17:43
  • Ah! This make sense. So does that mean the magnifying glass acts simultaneously as a convex and concave mirror? – uncreative May 15 '16 at 17:46
  • That is right.If you coat one of the surfaces, ( losing refraction/lens benefit) it can be seen more clearly. In fact if your question is *magnifying glass as mirrors?" it is still ok. – Narasimham Aug 19 '16 at 08:17

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When light goes from one medium to another some is reflected. You get a virtual upright image formed by reflection off the near surface of the glass and an inverted real image formed by reflection off the back surface.

M. Enns
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  • This make sense, but I just realized there are actually more than 2 reflections (in the picture there's actually three, the third being the bottom right). How is this so? – uncreative May 15 '16 at 17:58
  • Hmm, I couldn't see more than two with my magnifying glass. It could be that light is reflected multiple times and you are seeing an image formed by light initially reflected off the back then off the front and then off the back again. – M. Enns May 15 '16 at 18:05
  • Are there multiple types of images (virtual and upright, inverted and real) because one side is convex and the other is concave? – uncreative May 15 '16 at 18:15
  • That's right. Convex mirrors always produce upright, virtual images formed on the opposite side of the mirror as the object. Concave mirrors form real, inverted images on the same side of the mirror as the object if the object is farther than one focal length away from the mirror. – M. Enns May 15 '16 at 18:18