I am reading about lenses and I came across a post: What is exactly an ‘virtual object’ ? ( From the point of view of lens maker’s formula ) , which defines virtual object as follows-

"Virtual object" - is some where in the direction where the light ray is coming FROM, not where, it is going TO and so the virtual object and final image are not on the same side.

But my textbook is contradictory. According to my textbook, the virtual object and the image are on the same side. The following are screenshots from my textbook: enter image description here

enter image description here

So, which one is correct ?


If you meant a virtual image, this answer offers a very good explanation of what real and virtual images are.

In contrast, the term "virtual object" both from your textbook and the link you provided describe an intermediate object that WOULD BE the image IF only one refraction occured.

So possibly you, the link and the textbook are all right because you talk about different things (virtual image vs. virtual object). Anyway, in no case "the direction where the light comes from" plays a role in the explanation.

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  • $\begingroup$ So, in case of thin lenses (which involve 2 refractions) the virtual object is always on the same side of the image, right? $\endgroup$ – Gokulakrishnan Shankar Feb 28 '18 at 8:46
  • $\begingroup$ In case of convex lenses as described in the chapter you show, yes, the virtual object only takes into account the first refraction INTO the lens and will be to the right side of I. If, of course, $\mu_1$ < $\mu_2$. $\endgroup$ – Aziraphale Feb 28 '18 at 9:07

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