Question

When would virtual image produced by convex lens ? Why doesn't virtual image drawn on a screen ?

Answer 1

A converging lens produced a virtual image when the object is placed in front of the focal point. For such a position, the image is magnified and upright, thus allowing for easier viewing.

The light from the object has to fall on the screen after converging so that we can see the image on the screen. For plane mirrors, you can't get the virtual imageon a screen by putting the screen behind the mirror. The image that forms on your retina is the real image of the "virtual object" behind the mirror.