A diminished virtual image of a real object can be formed only by a

The correct answer is Option (2) → convex mirror

Option (1) plane mirror — Incorrect. A plane mirror forms its virtual image as far behind it as the object is in front, so \( v=-u \). The magnification \( m=-v/u \) is then 1. So the image has the same size as the object and is not diminished.

Option (2) convex mirror — Correct. For a convex mirror \( f \) is positive and a real object has \( u \) negative.

• The mirror equation gives \( 1/v=1/f+1/|u| \), so \( v \) is always positive. The image is behind the mirror and is virtual.

• The same equation makes \( v \) smaller than \( |u| \), so \( m=v/|u| \) is less than 1. The image is diminished for every position of the object.

Option (3) concave mirror — Incorrect. A concave mirror forms a virtual image only when the object lies between the pole and the focus. That image is farther from the mirror than the object, so it is enlarged.

Option (4) concave parabolic mirror — Incorrect. A parabolic mirror of this kind is still a concave, converging mirror. Like a concave spherical mirror, it gives a virtual image of a real object only when the object is inside its focus. That image is magnified.