Can you find the minimum limiting object distance for obtaining a real image ? What do you call this minimum limiting object distance ?

Why don't you get an image for certain object distances ?

The minimum distance from real object to a real image in a concave mirror is

What do you think a reading above normal limits indicates ?

An object is placed at a certain distance on the principal axis of a concave mirror. The image is formed at a distance of 30 cm from the mirror. Find the object distance if radius of curvature R = 15 cm