Virtual, erect, and magnified.
Explanation
A convex lens is a converging lens that generally forms real and inverted images. However, the nature, size, and orientation of the image depend strictly on the distance of the object from the optical center relative to the focal length ($f$).
Analysis:
When an object is placed within the focal length (between the optical center and the principal focus, i.e., $u < f$) of a convex lens:
- The refracted light rays diverge on the other side of the lens and do not intersect physically.
- To an observer, these rays appear to originate from a point on the same side of the lens as the object.
- Consequently, the image formed is virtual (cannot be projected on a screen), erect (upright), and magnified (larger than the object).
This specific property is the operating principle behind a simple microscope or a magnifying glass.
Key Takeaway:
A convex lens forms a virtual, erect, and magnified image only when the object is placed within its focal length. For all object positions at or beyond the focus, the image formed is real and inverted.