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I am trying to learn about optics and I am having a hard time understanding the meaning of "real" vs "virtual" image.

My understanding is that for a concave mirror, the image focuses on the same side as the object so it is a real image.

For a convex mirror, the image focuses on the opposite side of the object from the mirror so it is a virtual image.

However, we can both see either real or virtual images, so how are we seeing something that focuses on the other side of the mirror in the convex case ?

I am very confused.


marked as duplicate by Keep these mind, user10851, Emilio Pisanty, Qmechanic Nov 7 '13 at 21:55

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The distinction is very simple. A real image is one that the EM radiant energy (rays) actually pass through, so you can put a screen there, and see the image.

A virtual image is an imaginary image. No rays or EM radiation actually passes through it, so you can't see it on a screen placed there, it doesn't exist; you just think it is there. But you can photograph it, by putting a camera where the rays do emerge from, where you were able to see the virtual image with your eye.

Virtual, means it doesn't exist; it isn't real. For some crazy reason, people use "virtually" to mean, it is almost certain to be true; the exact opposite of what it really means.

  • 1
    $\begingroup$ I don't agree with your linguistic analysis (v1). "vir·tu·al adj. 1. Existing or resulting in essence or effect though not in actual fact, form, or name." $\endgroup$ – Keep these mind Nov 7 '13 at 20:35
  • $\begingroup$ While the term "virtual image" is of course in very wide use, I think that it may make more sense to think of it as a virtual subject. If one stands in front of a mirror holding a point light source, the light which reflects from the mirror will appear to come from a point light source behind the mirror. Since won't really appear to have passed through a point behind the mirror, I'm not sure why that point should be considered any sort of "image". Mirrors could create virtual images in cases where the thing which is reflected is actually an image, but that's not the most common scenario. $\endgroup$ – supercat Aug 6 '14 at 18:32
  • $\begingroup$ what you mean you can put a screen there and see the image ? $\endgroup$ – ado sar Feb 15 at 20:05

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