Read the following conversation.
Teacher: "If you want to collect the virtual images, which mirror do you select?".
Bharathi: "convex mirror"
Sowmya: "concave mirror"
Firoz: "plane mirror"
What do you think? Who is correct? Explain.
If we want a virtual image we will require a convex mirror and plane because :
A plane mirror will form an upright virtual image of the object with the same size.
A convex mirror will also form an upright virtual image but will appear smaller. Only a concave mirror can produce a real inverted image whose size depends on screen placement. If the real image and object are the same distance from the concave mirror, then they are both the same size. But if the real image is farther than the object is from the mirror, then the image is larger.
So it follows that if the real image is closer to the mirror than the object then it would be smaller. Also note that there is no real image with a concave mirror if you place the object inside the focal length of the mirror, in which case the image is virtual, upright, and bigger.
Hence, both Bharathi and Firoz are correct.