Re: Why do we see an upside-down image when we look at a magnifying glass?

Look at your magnifying glass from the side; wou will see a thin sheet
of glass, fatter in the centre than at the edges( concave)
 Now imagine a parallel beam of light entering the glass. Because it is
curved the beam is bent( refracted ) so that the edges of the beam meet
at a focal point. You look through it at a distance so the beam having
converged onto the focal point then diverges out again, but the beams
from the two edges have crossed, because they continue in stright lines.
Thus the image you see is of the beam of light reversed- ray from top of
glass now at bottom of your image and so on



[note added by MadSci Admin: There is actually a nice body
of previous answers in our archives dealing with lenses,
mirrors, and the images they produce.  Please search the
database using our search engine.]