For which position of the object does a convex lens form a virtual and erect image? Explain with the help of a ray diagram.

(N/A) convex lens forms a virtual and erect image when the object is placed between the optical centre $(O)$ and the principal focus $(F_1)$.
To explain this,consider two rays originating from the top of the object $(B)$: one ray moves parallel to the principal axis and passes through the focus $(F_2)$ after refraction,while the other ray passes through the optical centre $(O)$ without deviation.
When these two refracted rays are extended backwards,they appear to meet at a point $(B')$ on the same side of the lens as the object.
Thus,the image $(A'B')$ formed is virtual,erect,and magnified,and it lies on the same side as the object.