What type of lens would you use as a magnifying glass? How close must the object be to the lens?
Convex lens is a type of lens used as a magnifying glass. The object must be kept close, which will be within the focus of the lens (between the optical centre $C$ and the focus $F'$).
Explanation
When an object is placed at a distance less than the focus i.e., between optical centre, $C$ and focus, $F'$ of a convex lens, then the image formed is virtual, erect, larger than the object (enlarged or magnified), and behind the object (on the left side of the lens).
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