As we mentioned before, the nature of the image—that is, whether it’s real or
virtual—is determined by the side of the lens upon which the image is formed. If
the image is formed on the side of the lens that’s opposite the object, then the image
is real, and if the image is formed on the same side of the lens as the object, then
it’s virtual. Therefore, the image in Question 25 is real, while the image in Question
26 is virtual.
Which Side is Real?
For mirrors, the real side
(where so > 0) is the
same side as the object.
For lenses, the real side is
opposite the object.