Re: virtual images and convex lenses

[Robert Cohen <Robert.Cohen@PO-BOX.ESU.EDU>]

On Saturday, January 05, 2002 5:05 PM, John S. Denker wrote:
> [snip]
>
> Robert Cohen wrote:
> > I wear glasses
> > with diverging lens.  I'd say that *everything* I see is a
> virtual image.
> > If there is a problem with how I use "see" then is it
> possible to even "see"
> > objects?
>
> I don't object to this use of the word "see".
>
> But I think it is an abuse of the highly specific technical
> term "virtual image".
>
> Suppose you take off your glasses and look through a piece
> of window-glass.  Window glass is a completely non-image-forming
> system.  Does that mean you can't see anything?  I doubt it!
>
> To my way of thinking, the only image that really matters
> is the real image formed upon the retina.  In ordinary situations
> it is formed by the lens etc. of the eye, with perhaps a few percent
> of help from eyeglasses.

To my way of thinking, the image is there regardless of whether someone is
there to "record" it.

Is it incorrect to think of a piece of window-glass as obeying the thin lens
equation?
If not, is it incorrect to think of a piece of window-glass as having
f=infty?
If not, is it incorrect to think of a piece of window-glass as causing a
virtual image at the location of the object?
____________________________________________
Robert Cohen; rcohen@po-box.esu.edu; http://www.esu.edu/~bbq
Physics, East Stroudsburg Univ, E. Stroudsburg, PA 18301